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The Long History of mRNA Vaccines

Chris Beyrer

Messenger RNA, or mRNA, was discovered in the early 1960s; research into how mRNA could be delivered into cells was developed in the 1970s. So, why did it take until the global COVID-19 pandemic of 2020 for the first mRNA vaccine to be brought to market? 

In this explainer, Chris Beyrer talks us through mRNA vaccines’ history, development, and breakthroughs.

There’s a big gap between when the first mRNA flu vaccine was tested in mice in the 1990s and when the first mRNA vaccines for rabies were tested in humans in 2013. What was happening in the interim?

The early years of mRNA research were marked by a lot of enthusiasm for the technology but some difficult technical challenges that took a great deal of innovation to overcome. 

The biggest challenge was that mRNA would be taken up by the body and quickly degraded before it could “deliver” its message—the RNA transcript—and be read into proteins in the cells. 

The solution to this problem came from advances in nanotechnology: the development of fatty droplets (lipid nanoparticles) that wrapped the mRNA like a bubble, which allowed entry into the cells. Once inside the cell, the mRNA message could be translated into proteins, like the spike protein of SARS-CoV-2, and the immune system would then be primed to recognize the foreign protein. 

So, what happened once they figured out this technology?

The first mRNA vaccines using these fatty envelopes were developed against the deadly Ebola virus, but since that virus is only found in a limited number of African countries, it had no commercial development in the U.S.

Then COVID-19 hit … what happened then?

Remember, the COVID-19 pandemic spurred manufacturers to develop dozens of potential vaccines against SARS-CoV-2 and brought tremendous increases in funding. Some of those vaccines used traditional methods involving adenovirus as the spike protein delivery system—such as the Johnson & Johnson vector vaccine.

Thanks to decades of research and innovation, mRNA vaccine technology was ready. With COVID, this technology got its moment and has proven to be extremely safe and effective. Pfizer’s COVID-19 vaccine is the first mRNA product to achieve full FDA approval in the U.S.

What’s next?

Already, vaccine manufacturers are developing mRNA vaccines to protect against other respiratory viruses such as the flu. Moderna is exploring applications of the technology to protect against HIV. It’s a new era for vaccine technology and production, and a testament to scientific progress and decades of research.

Chris Beyrer, MD, MPH ’91 , is the Desmond M. Tutu Professor of Public Health and Human Rights and director of the Center for Public Health and Human Rights at the Johns Hopkins Bloomberg School of Public Health.

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• How to Update an mRNA Vaccine  
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Understanding COVID-19 mRNA Vaccines

Messenger RNA (mRNA) is a molecule that encodes a sequence that can be made into a protein. Scientists first learned about mRNA nearly 60 years ago, and researchers have been studying vaccines using mRNA for decades. The earliest COVID-19 vaccines authorized for use in the United States by the Food and Drug Administration (FDA) are mRNA vaccines.

• mRNA vaccines inject cells with instructions to generate a protein that is normally found on the surface of SARS-CoV-2, the virus that causes COVID-19.  
• The protein that the person makes in response to the vaccine can cause an immune response without a person ever having been exposed to the virus that causes COVID-19. Later, if the person is exposed to the virus, their immune system will recognize the virus and respond to it.  
• mRNA vaccines are safe and cannot alter your DNA, and you cannot get COVID-19 from the vaccine.  
• mRNA vaccines may seem to have arrived quickly, but this technology is built on decades of scientific research that have made these vaccines a reality.

How does an mRNA vaccine work?

mRNA acts as a cellular messenger. DNA, which is stored in a cell’s nucleus, encodes the genetic information for making proteins. mRNA transfers a copy of this genetic information outside of the nucleus, to a cell’s cytoplasm, where it is translated into amino acids by ribosomes and then folded into complete proteins. mRNA is a short-lived molecule, meaning it degrades easily and does not last long inside cells.

By injecting cells with a synthetic mRNA that encodes a viral spike protein, an mRNA vaccine can direct human cells to make a viral spike protein and evoke an immune response without a person ever having been exposed to the viral material.

These viral spike proteins, or antigens, normally coat the surface of the virus and are recognized by antibodies and other immune cells that prepare and protect the body against the virus. If a person is later exposed to the virus, antibodies and other parts of the immune system can recognize and attack the virus before it can infect healthy cells or cause illness.

How are mRNA vaccines different from traditional vaccines?

Traditional vaccines work by giving a person either viral proteins or an inactivated or weakened version of a virus that triggers an immune response. mRNA vaccines do not contain viral material. Instead, these vaccines contain lipid or fat bubbles that surround a segment of mRNA, which provide cells with the instructions to make a certain viral protein.

Can mRNA vaccines change your DNA?

No. There is no risk of an mRNA vaccine changing your DNA because mRNA does not have the ability to alter DNA. Your cells constantly make their own mRNA. The synthetic mRNA in the vaccine acts like any other mRNA that your cells make.

Are FDA-approved mRNA vaccines safe and effective?

Yes. The FDA approval process involves careful review of clinical trial data to independently confirm that a vaccine is safe and effective. Two mRNA vaccines have been tested in large-scale clinical trials that included elderly and medically at-risk individuals; 30% of participants in these trials were from racially and ethnically diverse backgrounds. Both vaccines have reported to result in a range of minor side effects, such as flu-like symptoms, that resolve within one or two days. mRNA vaccines do not contain the SARS-CoV-2 virus, so you cannot get COVID-19 from an mRNA vaccine.

How have mRNA vaccines been produced so rapidly?

One of the most exciting aspects of mRNA technology is how rapidly it can be developed to target a particular virus. While traditional vaccines can take years, creating an mRNA-based vaccine that targets a newly discovered virus can be accomplished in a short period of time (days to weeks to make the new vaccine candidate) and primarily requires knowledge of the viral genetic code. This greatly speeds up vaccine development. mRNA vaccines are built on decades of scientific research. For example, NHGRI has long supported research into the development of nucleotide synthesis technologies that allowed for the creation of synthetic RNA and DNA. With the viral sequence in hand, these technologies have been used to make mRNA vaccines a rapid reality.

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Last updated: August 30, 2021

Development of mRNA Vaccines: Scientific and Regulatory Issues

Affiliations.

• 1 Department of Health Product Policy and Standards, World Health Organization, Avenue Appia 20, CH-1211 Geneva, Switzerland.
• 2 ProTherImmune 3656 Happy Valley Road, Lafayette, CA 94549, USA.
• 3 Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, US Food & Drug Administration, Silver Spring, MD 20993, USA.
• PMID: 33498787
• PMCID: PMC7910833
• DOI: 10.3390/vaccines9020081

The global research and development of mRNA vaccines have been prodigious over the past decade, and the work in this field has been stimulated by the urgent need for rapid development of vaccines in response to an emergent disease such as the current COVID-19 pandemic. Nevertheless, there remain gaps in our understanding of the mechanism of action of mRNA vaccines, as well as their long-term performance in areas such as safety and efficacy. This paper reviews the technologies and processes used for developing mRNA prophylactic vaccines, the current status of vaccine development, and discusses the immune responses induced by mRNA vaccines. It also discusses important issues with regard to the evaluation of mRNA vaccines from regulatory perspectives. Setting global norms and standards for biologicals including vaccines to assure their quality, safety and efficacy has been a WHO mandate and a core function for more than 70 years. New initiatives are ongoing at WHO to arrive at a broad consensus to formulate international guidance on the manufacture and quality control, as well as nonclinical and clinical evaluation of mRNA vaccines, which is deemed necessary to facilitate international convergence of manufacturing and regulatory practices and provide support to National Regulatory Authorities in WHO member states.

Keywords: WHO standards; mRNA vaccines; prophylactic vaccines; regulatory considerations; vaccine development.

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Brain cancer in children is notoriously hard to treat – a new mRNA cancer vaccine triggers an attack from within

Assistant Professor of Neurosurgery, University of Florida

Assistant Professor of Hematology, University of Florida

Disclosure statement

John Ligon receives funding from the V Foundation, MIB Agents, the National Pediatric Cancer Foundation, Hyundai Hope on Wheels, the Pediatric Cancer Research Foundation, the Children's Miracle Network, the ChadTough Defeat DIPG Foundation, the Children's Cancer Research Fund, the DIPG/DMG Research Funding Alliance, the National Cancer Institute, and the Florida Department of Health Live Like Bella Pediatric Cancer Research Initiative.

Christina von Roemeling does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

University of Florida provides funding as a founding partner of The Conversation US.

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Brain cancers remain among the most challenging tumors to treat. They often don’t respond to traditional treatments because many chemotherapies are unable to penetrate the protective barrier around the brain. Other treatments like radiation and surgery can leave patients with lifelong debilitating side effects .

As a result, brain cancer is the leading cause of cancer-related death in children . Brain tumors in children frequently do not respond to treatments developed for adults, likely due to the fact that pediatric brain cancers are not as well-studied as adult brain cancers. There is an urgent need to develop new treatments specific to children.

We developed a new messenger-RNA, or mRNA, cancer vaccine, described in newly published research , that can deliver treatments more effectively in children who have brain cancer and teach their immune systems to fight back.

How do cancer vaccines work?

The immune system is a complex network of cells, tissues and organs whose primary function is to continuously surveil the body for threats posed by foreign invaders – pathogens that damage tissues and make you sick. It accomplishes this by recognizing antigens, or abnormal proteins or molecules, on pathogens. T cells that recognize these antigens seek out and destroy the pathogens.

Your immune system also protects you from domestic threats like cancer . Over time, your cells sustain DNA damage from either internal or external stressors, leading to mutations. The proteins and molecules produced from mutated DNA look quite different from the ones cells typically produce, so your immune system can recognize them as antigens. Cancer develops when cells accumulate mutations that enable them to continue to grow and divide while simultaneously going undetected by the immune system.

In 1991, scientists identified the first tumor antigen , helping lay the framework for modern-day immunotherapy. Since then, researchers have identified many new tumor antigens, facilitating the development of cancer vaccines. Broadly, cancer vaccines deliver tumor antigens into the body to teach the immune system to recognize and attack cancer cells that display those antigens. Although all cancer vaccines conceptually work very similarly, they each significantly vary in the way they are developed and the number and combination of antigens they carry.

One of the biggest differences among cancer vaccines is how they are created. Some vaccines use protein fragments, or peptides , of tumor antigens that are directly given to patients. Other vaccines use viruses reengineered to express cancer antigens. Even more complex are vaccines where a patient’s own immune cells are collected and trained to recognize cancer antigens in a laboratory before being delivered back to the patient.

Currently, there is a lot of excitement and focus among researchers on developing mRNA-based cancer vaccines . Whereas DNA is the blueprint of which proteins to make, mRNA is a copy of the blueprint that tells cells how to build these proteins. Thus, researchers can use mRNA to create blueprint copies of potential antigens.

mRNA cancer vaccines

The COVID-19 pandemic brought significant attention to the potential of using mRNA-based vaccines to stimulate the immune system and provide protection against the antigens they encode for. But researchers have been investigating the use of mRNA vaccines for treating various cancers since before the pandemic.

Our team of scientists in the Brain Tumor Immunotherapy Program at University of Florida has spent the past 10 years developing and optimizing mRNA vaccines to treat brain cancer.

Cancer vaccines have faced significant challenges . One key hurdle is that these vaccines may not always trigger a strong enough immune response to eradicate the cancer completely. Moreover, tumors are not made up of one type of cancer cell, but rather a complex mix of cancer cells that each harbors its own unique cocktail of mutations.

Our cancer vaccine seeks to address these issues in a number of ways.

First, we designed our vaccines by using the RNA of a patients’ own cancer cells as a template for the mRNA inside our nanoparticles. We also packaged our cancer vaccine inside of nanoparticles made up of specialized lipids, or fat molecules. We maximized the amount of mRNA packaged within each nanoparticle by sandwiching them between lipid layers like the layers of an onion. In this way, we increase the likelihood that the mRNA molecules in our nanoparticles produce enough tumor antigens from that patient’s cancer to activate an immune response.

Also, instead of injecting nanoparticles into the skin, muscle or directly into the tumor, as is commonly done for many therapeutic cancer vaccines, our mRNA nanoparticles are injected into the bloodstream . From there, they travel to organs throughout the body involved in the immune response to teach the body to fight against the cancer. By doing so, we’ve found that the immune system launches a near immediate and powerful response. Within six hours of receiving the vaccine, there is a significant increase in the amount of blood markers connected to immune activation.

Looking to the future

Our mRNA-based vaccines are currently undergoing early-phase clinical trials to treat real patients with brain cancer.

We administered our mRNA-based vaccine to four adult patients with glioblastoma who had relapsed after previous treatment. All patients survived several months longer than the expected average survival at this advanced stage of illness. We expect to treat children with a type of brain tumor called pediatric high-grade glioma by the end of the year.

Importantly, mRNA vaccines can be developed to treat any kind of cancer, including childhood brain tumors. Our Pediatric Cancer Immunotherapy Initiative focuses on developing new immune-based therapies for children afflicted with cancer. After developing an mRNA vaccine for glioma in chidren, we will expand to treat other kinds of pediatric brain cancers like medulloblastoma and potentially treat other kinds of cancers like skin cancer and bone cancer.

We are hopeful that mRNA-based vaccines may lead to more children being cured of their brain tumors.

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• Pediatric cancer
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Thousands Believe Covid Vaccines Harmed Them. Is Anyone Listening?

All vaccines have at least occasional side effects. But people who say they were injured by Covid vaccines believe their cases have been ignored.

Shaun Barcavage, 54, a nurse practitioner in New York City, said that ever since his first Covid shot, standing up has sent his heart racing. Credit... Hannah Yoon for The New York Times

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By Apoorva Mandavilli

Apoorva Mandavilli spent more than a year talking to dozens of experts in vaccine science, policymakers and people who said they had experienced serious side effects after receiving a Covid-19 vaccine.

• Published May 3, 2024 Updated May 4, 2024

Within minutes of getting the Johnson & Johnson Covid-19 vaccine, Michelle Zimmerman felt pain racing from her left arm up to her ear and down to her fingertips. Within days, she was unbearably sensitive to light and struggled to remember simple facts.

She was 37, with a Ph.D. in neuroscience, and until then could ride her bicycle 20 miles, teach a dance class and give a lecture on artificial intelligence, all in the same day. Now, more than three years later, she lives with her parents. Eventually diagnosed with brain damage, she cannot work, drive or even stand for long periods of time.

“When I let myself think about the devastation of what this has done to my life, and how much I’ve lost, sometimes it feels even too hard to comprehend,” said Dr. Zimmerman, who believes her injury is due to a contaminated vaccine batch .

The Covid vaccines, a triumph of science and public health, are estimated to have prevented millions of hospitalizations and deaths . Yet even the best vaccines produce rare but serious side effects . And the Covid vaccines have been given to more than 270 million people in the United States, in nearly 677 million doses .

Dr. Zimmerman’s account is among the more harrowing, but thousands of Americans believe they suffered serious side effects following Covid vaccination. As of April, just over 13,000 vaccine-injury compensation claims have been filed with the federal government — but to little avail. Only 19 percent have been reviewed. Only 47 of those were deemed eligible for compensation, and only 12 have been paid out, at an average of about $3,600 .

Some scientists fear that patients with real injuries are being denied help and believe that more needs to be done to clarify the possible risks.

“At least long Covid has been somewhat recognized,” said Akiko Iwasaki, an immunologist and vaccine expert at Yale University. But people who say they have post-vaccination injuries are “just completely ignored and dismissed and gaslighted,” she added.

In interviews and email exchanges conducted over several months, federal health officials insisted that serious side effects were extremely rare and that their surveillance efforts were more than sufficient to detect patterns of adverse events.

“Hundreds of millions of people in the United States have safely received Covid vaccines under the most intense safety monitoring in U.S. history,” Jeff Nesbit, a spokesman for the Department of Health and Human Services, said in an emailed statement.

But in a recent interview, Dr. Janet Woodcock, a longtime leader of the Food and Drug Administration, who retired in February, said she believed that some recipients had experienced uncommon but “serious” and “life-changing” reactions beyond those described by federal agencies.

“I feel bad for those people,” said Dr. Woodcock, who became the F.D.A.’s acting commissioner in January 2021 as the vaccines were rolling out. “I believe their suffering should be acknowledged, that they have real problems, and they should be taken seriously.”

“I’m disappointed in myself,” she added. “I did a lot of things I feel very good about, but this is one of the few things I feel I just didn’t bring it home.”

Federal officials and independent scientists face a number of challenges in identifying potential vaccine side effects.

The nation’s fragmented health care system complicates detection of very rare side effects, a process that depends on an analysis of huge amounts of data. That’s a difficult task when a patient may be tested for Covid at Walgreens, get vaccinated at CVS, go to a local clinic for minor ailments and seek care at a hospital for serious conditions. Each place may rely on different health record systems.

There is no central repository of vaccine recipients, nor of medical records, and no easy to way to pool these data. Reports to the largest federal database of so-called adverse events can be made by anyone, about anything. It’s not even clear what officials should be looking for.

“I mean, you’re not going to find ‘brain fog’ in the medical record or claims data, and so then you’re not going to find” a signal that it may be linked to vaccination, Dr. Woodcock said. If such a side effect is not acknowledged by federal officials, “it’s because it doesn’t have a good research definition,” she added. “It isn’t, like, malevolence on their part.”

The government’s understaffed compensation fund has paid so little because it officially recognizes few side effects for Covid vaccines. And vaccine supporters, including federal officials, worry that even a whisper of possible side effects feeds into misinformation spread by a vitriolic anti-vaccine movement.

‘I’m Not Real’

Patients who believe they experienced serious side effects say they have received little support or acknowledgment.

Shaun Barcavage, 54, a nurse practitioner in New York City who has worked on clinical trials for H.I.V. and Covid, said that ever since his first Covid shot, merely standing up sent his heart racing — a symptom suggestive of postural orthostatic tachycardia syndrome , a neurological disorder that some studies have linked to both Covid and, much less often, vaccination .

He also experienced stinging pain in his eyes, mouth and genitals, which has abated, and tinnitus, which has not.

“I can’t get the government to help me,” Mr. Barcavage said of his fruitless pleas to federal agencies and elected representatives. “I am told I’m not real. I’m told I’m rare. I’m told I’m coincidence.”

Renee France, 49, a physical therapist in Seattle, developed Bell’s palsy — a form of facial paralysis, usually temporary — and a dramatic rash that neatly bisected her face. Bell’s palsy is a known side effect of other vaccines, and it has been linked to Covid vaccination in some studies.

But Dr. France said doctors were dismissive of any connection to the Covid vaccines. The rash, a bout of shingles, debilitated her for three weeks, so Dr. France reported it to federal databases twice.

“I thought for sure someone would reach out, but no one ever did,” she said.

Similar sentiments were echoed in interviews, conducted over more than a year, with 30 people who said they had been harmed by Covid shots. They described a variety of symptoms following vaccination, some neurological, some autoimmune, some cardiovascular.

All said they had been turned away by physicians, told their symptoms were psychosomatic, or labeled anti-vaccine by family and friends — despite the fact that they supported vaccines.

Even leading experts in vaccine science have run up against disbelief and ambivalence.

Dr. Gregory Poland, 68, editor in chief of the journal Vaccine, said that a loud whooshing sound in his ears had accompanied every moment since his first shot, but that his entreaties to colleagues at the Centers for Disease Control and Prevention to explore the phenomenon, tinnitus, had led nowhere.

He received polite responses to his many emails, but “I just don’t get any sense of movement,” he said.

“If they have done studies, those studies should be published,” Dr. Poland added. In despair that he might “never hear silence again,” he has sought solace in meditation and his religious faith.

Dr. Buddy Creech, 50, who led several Covid vaccine trials at Vanderbilt University, said his tinnitus and racing heart lasted about a week after each shot. “It’s very similar to what I experienced during acute Covid, back in March of 2020,” Dr. Creech said.

Research may ultimately find that most reported side effects are unrelated to the vaccine, he acknowledged. Many can be caused by Covid itself.

“Regardless, when our patients experience a side effect that may or may not be related to the vaccine, we owe it to them to investigate that as completely as we can,” Dr. Creech said.

Federal health officials say they do not believe that the Covid vaccines caused the illnesses described by patients like Mr. Barcavage, Dr. Zimmerman and Dr. France. The vaccines may cause transient reactions, such as swelling, fatigue and fever, according to the C.D.C., but the agency has documented only four serious but rare side effects .

Two are associated with the Johnson & Johnson vaccine, which is no longer available in the United States: Guillain-Barré syndrome , a known side effect of other vaccines , including the flu shot; and a blood-clotting disorder.

The C.D.C. also links mRNA vaccines made by Pfizer-BioNTech and Moderna to heart inflammation, or myocarditis, especially in boys and young men. And the agency warns of anaphylaxis, or severe allergic reaction, which can occur after any vaccination.

Listening for Signals

Agency scientists are monitoring large databases containing medical information on millions of Americans for patterns that might suggest a hitherto unknown side effect of vaccination, said Dr. Demetre Daskalakis, director of the C.D.C.’s National Center for Immunization and Respiratory Diseases.

“We toe the line by reporting the signals that we think are real signals and reporting them as soon as we identify them as signals,” he said. The agency’s systems for monitoring vaccine safety are “pretty close” to ideal, he said.

Those national surveillance efforts include the Vaccine Adverse Event Reporting System (VAERS). It is the largest database, but also the least reliable: Reports of side effects can be submitted by anyone and are not vetted, so they may be subject to bias or manipulation.

The system contains roughly one million reports regarding Covid vaccination, the vast majority for mild events, according to the C.D.C.

Federal researchers also comb through databases that combine electronic health records and insurance claims on tens of millions of Americans. The scientists monitor the data for 23 conditions that may occur following Covid vaccination. Officials remain alert to others that may pop up, Dr. Daskalakis said.

But there are gaps, some experts noted. The Covid shots administered at mass vaccination sites were not recorded in insurance claims databases, for example, and medical records in the United States are not centralized.

“It’s harder to see signals when you have so many people, and things are happening in different parts of the country, and they’re not all collected in the same system,” said Rebecca Chandler, a vaccine safety expert at the Coalition for Epidemic Preparedness Innovations.

An expert panel convened by the National Academies concluded in April that for the vast majority of side effects, there was not enough data to accept or reject a link.

Asked at a recent congressional hearing whether the nation’s vaccine-safety surveillance was sufficient, Dr. Peter Marks, director of the F.D.A.’s Center for Biologics Evaluation and Research, said, “I do believe we could do better.”

In some countries with centralized health care systems, officials have actively sought out reports of serious side effects of Covid vaccines and reached conclusions that U.S. health authorities have not.

In Hong Kong, the government analyzed centralized medical records of patients after vaccination and paid people to come forward with problems. The strategy identified “a lot of mild cases that other countries would not otherwise pick up,” said Ian Wong, a researcher at the University of Hong Kong who led the nation’s vaccine safety efforts.

That included the finding that in rare instances — about seven per million doses — the Pfizer-BioNTech vaccine triggered a bout of shingles serious enough to require hospitalization.

The European Medicines Agency has linked the Pfizer and Moderna vaccines to facial paralysis, tingling sensations and numbness. The E.M.A. also counts tinnitus as a side effect of the Johnson & Johnson vaccine, although the American health agencies do not. There are more than 17,000 reports of tinnitus following Covid vaccination in VAERS.

Are the two linked? It’s not clear. As many as one in four adults has some form of tinnitus. Stress, anxiety, grief and aging can lead to the condition, as can infections like Covid itself and the flu.

There is no test or scan for tinnitus, and scientists cannot easily study it because the inner ear is tiny, delicate and encased in bone, said Dr. Konstantina Stankovic, an otolaryngologist at Stanford University.

Still, an analysis of health records from nearly 2.6 million people in the United States found that about 0.04 percent , or about 1,000, were diagnosed with tinnitus within three weeks of their first mRNA shot. In March, researchers in Australia published a study linking tinnitus and vertigo to the vaccines .

The F.D.A. is monitoring reports of tinnitus, but “at this time, the available evidence does not suggest a causal association with the Covid-19 vaccines,” the agency said in a statement.

Despite surveillance efforts, U.S. officials were not the first to identify a significant Covid vaccine side effect: myocarditis in young people receiving mRNA vaccines. It was Israeli authorities who first raised the alarm in April 2021. Officials in the United States said at the time that they had not seen a link.

On May 22, 2021, news broke that the C.D.C. was investigating a “relatively few” cases of myocarditis. By June 23, the number of myocarditis reports in VAERS had risen to more than 1,200 — a hint that it is important to tell doctors and patients what to look for.

Later analyses showed that the risk for myocarditis and pericarditis, a related condition, is highest after a second dose of an mRNA Covid vaccine in adolescent males aged 12 to 17 years.

In many people, vaccine-related myocarditis is transient. But some patients continue to experience pain, breathlessness and depression, and some show persistent changes on heart scans . The C.D.C. has said there were no confirmed deaths related to myocarditis, but in fact there have been several accounts of deaths reported post-vaccination .

Pervasive Misinformation

The rise of the anti-vaccine movement has made it difficult for scientists, in and out of government, to candidly address potential side effects, some experts said. Much of the narrative on the purported dangers of Covid vaccines is patently false, or at least exaggerated, cooked up by savvy anti-vaccine campaigns.

Questions about Covid vaccine safety are core to Robert F. Kennedy Jr.’s presidential campaign. Citing debunked theories about altered DNA, Florida’s surgeon general has called for a halt to Covid vaccination in the state.

“The sheer nature of misinformation, the scale of misinformation, is staggering, and anything will be twisted to make it seem like it’s not just a devastating side effect but proof of a massive cover-up,” said Dr. Joshua Sharfstein, a vice dean at Johns Hopkins University.

Among the hundreds of millions of Americans who were immunized for Covid, some number would have had heart attacks or strokes anyway. Some women would have miscarried. How to distinguish those caused by the vaccine from those that are coincidences? The only way to resolve the question is intense research .

But the National Institutes of Health is conducting virtually no studies on Covid vaccine safety, several experts noted. William Murphy, a cancer researcher who worked at the N.I.H. for 12 years, has been prodding federal health officials to initiate these studies since 2021.

The officials each responded with “that very tired mantra: ‘But the virus is worse,’” Dr. Murphy recalled. “Yes, the virus is worse, but that doesn’t obviate doing research to make sure that there may be other options.”

A deeper understanding of possible side effects, and who is at risk for them, could have implications for the design of future vaccines, or may indicate that for some young and healthy people, the benefit of Covid shots may no longer outweigh the risks — as some European countries have determined.

Thorough research might also speed assistance to thousands of Americans who say they were injured.

The federal government has long run the National Vaccine Injury Compensation Program , designed to compensate people who suffer injuries after vaccination. Established more than three decades ago, the program sets no limit on the amounts awarded to people found to have been harmed.

But Covid vaccines are not covered by that fund because Congress has not made them subject to the excise tax that pays for it. Some lawmakers have introduced bills to make the change.

Instead, claims regarding Covid vaccines go to the Countermeasures Injury Compensation Program . Intended for public health emergencies, this program has narrow criteria to pay out and sets a limit of $50,000, with stringent standards of proof.

It requires applicants to prove within a year of the injury that it was “the direct result” of getting the Covid vaccine, based on “compelling, reliable, valid, medical, and scientific evidence.”

The program had only four staff members at the beginning of the pandemic, and now has 35 people evaluating claims. Still, it has reviewed only a fraction of the 13,000 claims filed, and has paid out only a dozen.

Dr. Ilka Warshawsky, a 58-year-old pathologist, said she lost all hearing in her right ear after a Covid booster shot. But hearing loss is not a recognized side effect of Covid vaccination.

The compensation program for Covid vaccines sets a high bar for proof, she said, yet offers little information on how to meet it: “These adverse events can be debilitating and life-altering, and so it’s very upsetting that they’re not acknowledged or addressed.”

Dr. Zimmerman, the neuroscientist, submitted her application in October 2021 and provided dozens of supporting medical documents. She received a claim number only in January 2023.

In adjudicating her claim for workers’ compensation, Washington State officials accepted that Covid vaccination caused her injury, but she has yet to get a decision from the federal program.

One of her therapists recently told her she might never be able to live independently again.

“That felt like a devastating blow,” Dr. Zimmerman said. “But I’m trying not to lose hope there will someday be a treatment and a way to cover it.”

Apoorva Mandavilli is a reporter focused on science and global health. She was a part of the team that won the 2021 Pulitzer Prize for Public Service for coverage of the pandemic. More about Apoorva Mandavilli

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New mRNA cancer vaccine triggers fierce immune response to fight malignant brain tumor

In a first-ever human clinical trial of four adult patients, an mRNA cancer vaccine developed at the University of Florida quickly reprogrammed the immune system to attack glioblastoma, the most aggressive and lethal brain tumor.

The results mirror those in 10 pet dog patients suffering from naturally occurring brain tumors whose owners approved of their participation, as they had no other treatment options, as well as results from preclinical mouse models. The breakthrough now will be tested in a Phase 1 pediatric clinical trial for brain cancer.

Reported May 1 in the journal Cell , the discovery represents a potential new way to recruit the immune system to fight notoriously treatment-resistant cancers using an iteration of mRNA technology and lipid nanoparticles, similar to COVID-19 vaccines, but with two key differences: use of a patient's own tumor cells to create a personalized vaccine, and a newly engineered complex delivery mechanism within the vaccine.

"Instead of us injecting single particles, we're injecting clusters of particles that are wrapping around each other like onions, like a bag full of onions," said senior author Elias Sayour, M.D., Ph.D., a UF Health pediatric oncologist who pioneered the new vaccine, which like other immunotherapies attempts to "educate" the immune system that a tumor is foreign. "And the reason we've done that in the context of cancer is these clusters alert the immune system in a much more profound way than single particles would."

Among the most impressive findings was how quickly the new method, delivered intravenously, spurred a vigorous immune-system response to reject the tumor, said Sayour, principal investigator of the RNA Engineering Laboratory within UF's Preston A. Wells Jr. Center for Brain Tumor Therapy and a UF Health Cancer Center and McKnight Brain Institute investigator who led the multi-institution research team.

"In less than 48 hours, we could see these tumors shifting from what we refer to as 'cold' -- immune cold, very few immune cells, very silenced immune response -- to 'hot,' very active immune response," he said. "That was very surprising given how quick this happened, and what that told us is we were able to activate the early part of the immune system very rapidly against these cancers, and that's critical to unlock the later effects of the immune response."

Glioblastoma is among the most devastating diagnoses, with median survival around 15 months. Current standard of care involves surgery, radiation and some combination of chemotherapy.

The new publication is the culmination of promising translational results over seven years of studies, starting in preclinical mouse models and then in a clinical trial of 10 pet dogs that had spontaneously developed terminal brain cancer and had no other treatment options. That trial was conducted with owners' consent in collaboration with the UF College of Veterinary Medicine. Dogs offer a naturally occurring model for malignant glioma because they are the only other species that develops spontaneous brain tumors with some frequency, said Sheila Carrera-Justiz, D.V.M., a veterinary neurologist at the UF College of Veterinary Medicine who is partnering with Sayour on the clinical trials. Gliomas in dogs are universally terminal, she said.

After treating pet dogs that had spontaneously developed brain cancer with personalized mRNA vaccines, Sayour's team advanced the research to a small Food and Drug Administration-approved clinical trial designed to ensure safety and test feasibility before expanding to a larger trial.

In a cohort of four patients, genetic material called RNA was extracted from each patient's own surgically removed tumor, and then messenger RNA, or mRNA -- the blueprint of what is inside every cell, including tumor cells -- was amplified and wrapped in the newly designed high-tech packaging of biocompatible lipid nanoparticles, to make tumor cells "look" like a dangerous virus when reinjected into the bloodstream and prompt an immune-system response. The vaccine was personalized to each patient with a goal of getting the most out of their unique immune system.

"The demonstration that making an mRNA cancer vaccine in this fashion generates similar and strong responses across mice, pet dogs that have developed cancer spontaneously and human patients with brain cancer is a really important finding, because oftentimes we don't know how well the preclinical studies in animals are going to translate into similar responses in patients," said Duane Mitchell, M.D., Ph.D., director of the UF Clinical and Translational Science Institute and the UF Brain Tumor Immunotherapy Program and a co-author of the paper. "And while mRNA vaccines and therapeutics are certainly a hot topic since the COVID pandemic, this is a novel and unique way of delivering the mRNA to generate these really significant and rapid immune responses that we're seeing across animals and humans."

While too early in the trial to assess the clinical effects of the vaccine, the patients either lived disease-free longer than expected or survived longer than expected.

The 10 pet dogs lived a median of 139 days, compared with a median survival of 30 to 60 days typical for dogs with the condition.

The next step, through support from the Food and Drug Administration and the CureSearch for Children's Cancer foundation, will be an expanded Phase I clinical trial to include up to 24 adult and pediatric patients to validate the findings. Once an optimal and safe dose is confirmed, an estimated 25 children would participate in Phase 2, said Sayour, an associate professor in the Lillian S. Wells Department of Neurosurgery and the department of pediatrics in the UF College of Medicine, part of UF Health.

For the new clinical trial, Sayour's lab will partner with a multi-institution consortium, the Pediatric Neuro-Oncology Consortium, to send the immunotherapy treatment to children's hospitals across the country. They will do this by receiving an individual patient's tumor, manufacturing the personalized vaccine at UF and sending it back to the patient's medical team, said Sayour, co-leader of the Immuno-Oncology and Microbiome research program at the UF Health Cancer Center.

Despite the promising results, the authors said one limitation is continued uncertainty about how best to harness the immune system while minimizing the potential for adverse side effects.

"I am hopeful that this could be a new paradigm for how we treat patients, a new platform technology for how we can modulate the immune system," Sayour said. "I am hopeful for how this could now synergize with other immunotherapies and perhaps unlock those immunotherapies. We showed in this paper that you actually can have synergy with other types of immunotherapies, so maybe now we can have a combination approach of immunotherapy."

Sayour and Mitchell hold patents related to the vaccine which are under option to license by iOncologi Inc., a biotech company born as a "spin out" from UF in which Mitchell holds interest.

• Brain Tumor
• Immune System
• Diseases and Conditions
• Neuroscience
• Brain-Computer Interfaces
• Mental Health
• Immune system
• Monoclonal antibody therapy
• Renal cell carcinoma
• Malignant melanoma

Story Source:

Materials provided by University of Florida . Original written by Michelle Jaffee. Note: Content may be edited for style and length.

Journal Reference :

• Hector R. Mendez-Gomez, Anna DeVries, Paul Castillo, Christina von Roemeling, Sadeem Qdaisat, Brian D. Stover, Chao Xie, Frances Weidert, Chong Zhao, Rachel Moor, Ruixuan Liu, Dhruvkumar Soni, Elizabeth Ogando-Rivas, Jonathan Chardon-Robles, James McGuiness, Dingpeng Zhang, Michael C. Chung, Christiano Marconi, Stephen Michel, Arnav Barpujari, Gabriel W. Jobin, Nagheme Thomas, Xiaojie Ma, Yodarlynis Campaneria, Adam Grippin, Aida Karachi, Derek Li, Bikash Sahay, Leighton Elliott, Timothy P. Foster, Kirsten E. Coleman, Rowan J. Milner, W. Gregory Sawyer, John A. Ligon, Eugenio Simon, Brian Cleaver, Kristine Wynne, Marcia Hodik, Annette M. Molinaro, Juan Guan, Patrick Kellish, Andria Doty, Ji-Hyun Lee, Tara Massini, Jesse L. Kresak, Jianping Huang, Eugene I. Hwang, Cassie Kline, Sheila Carrera-Justiz, Maryam Rahman, Sebastian Gatica, Sabine Mueller, Michael Prados, Ashley P. Ghiaseddin, Natalie L. Silver, Duane A. Mitchell, Elias J. Sayour. RNA aggregates harness the danger response for potent cancer immunotherapy . Cell , 2024; DOI: 10.1016/j.cell.2024.04.003

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Cancer vaccines are having a renaissance

After years of lackluster results, cancer vaccines seem poised for success. Finally.

• Cassandra Willyard archive page

This article first appeared in The Checkup,  MIT Technology Review’s  weekly biotech newsletter. To receive it in your inbox every Thursday, and read articles like this first,  sign up here .  

Last week, Moderna and Merck launched a large clinical trial in the UK of a promising new cancer therapy: a personalized vaccine that targets a specific set of mutations found in each individual’s tumor. This study is enrolling patients with melanoma. But the companies have also launched a phase III trial for lung cancer. And earlier this month BioNTech and Genentech announced that a personalized vaccine they developed in collaboration shows promise in pancreatic cancer, which has a notoriously poor survival rate.

Drug developers have been working for decades on vaccines to help the body’s immune system fight cancer, without much success. But promising results in the past year suggest that the strategy may be reaching a turning point. Will these therapies finally live up to their promise?

This week in The Checkup, let’s talk cancer vaccines. (And, you guessed it, mRNA.)

Long before companies leveraged mRNA to fight covid, they were developing mRNA vaccines to combat cancer. BioNTech delivered its first mRNA vaccines to people with treatment-resistant melanoma nearly a decade ago. But when the pandemic hit, development of mRNA vaccines jumped into warp drive. Now dozens of trials are underway to test whether these shots can transform cancer the way they did covid. 

Recent news has some experts cautiously optimistic. In December, Merck and Moderna announced results from an earlier trial that included 150 people with melanoma who had undergone surgery to have their cancer removed. Doctors administered nine doses of the vaccine over about six months, as well as  what’s known as an immune checkpoint inhibitor. After three years of follow-up, the combination had cut the risk of recurrence or death by almost half compared with the checkpoint inhibitor alone.

The new results reported by BioNTech and Genentech, from a small trial of 16 patients with pancreatic cancer, are equally exciting. After surgery to remove the cancer, the participants received immunotherapy, followed by the cancer vaccine and a standard chemotherapy regimen. Half of them responded to the vaccine, and three years after treatment, six of those people still had not had a recurrence of their cancer. The other two had relapsed. Of the eight participants who did not respond to the vaccine, seven had relapsed. Some of these patients might not have responded  because they lacked a spleen, which plays an important role in the immune system. The organ was removed as part of their cancer treatment. 

The hope is that the strategy will work in many different kinds of cancer. In addition to pancreatic cancer, BioNTech’s personalized vaccine is being tested in colorectal cancer, melanoma, and metastatic cancers.

The purpose of a cancer vaccine is to train the immune system to better recognize malignant cells, so it can destroy them. The immune system has the capacity to clear cancer cells if it can find them. But tumors are slippery. They can hide in plain sight and employ all sorts of tricks to evade our immune defenses. And cancer cells often look like the body’s own cells because, well, they are the body’s own cells.

There are differences between cancer cells and healthy cells, however. Cancer cells acquire mutations that help them grow and survive, and some of those mutations give rise to proteins that stud the surface of the cell—so-called neoantigens.

Personalized cancer vaccines like the ones Moderna and BioNTech are developing are tailored to each patient’s particular cancer. The researchers collect a piece of the patient’s tumor and a sample of healthy cells. They sequence these two samples and compare them in order to identify mutations that are specific to the tumor. Those mutations are then fed into an AI algorithm that selects those most likely to elicit an immune response. Together these neoantigens form a kind of police sketch of the tumor, a rough picture that helps the immune system recognize cancerous cells.  

“A lot of immunotherapies stimulate the immune response in a nonspecific way—that is, not directly against the cancer,” said Patrick Ott, director of the Center for Personal Cancer Vaccines at the Dana-Farber Cancer Institute, in a 2022 interview .  “Personalized cancer vaccines can direct the immune response to exactly where it needs to be.”

How many neoantigens do you need to create that sketch?  “We don’t really know what the magical number is,” says Michelle Brown, vice president of individualized neoantigen therapy at Moderna. Moderna’s vaccine has 34. “It comes down to what we could fit on the mRNA strand, and it gives us multiple shots to ensure that the immune system is stimulated in the right way,” she says. BioNTech is using 20.

The neoantigens are put on an mRNA strand and injected into the patient. From there, they are taken up by cells and translated into proteins, and those proteins are expressed on the cell’s surface, raising an immune response

mRNA isn’t the only way to teach the immune system to recognize neoantigens. Researchers are also delivering neoantigens as DNA, as peptides, or via immune cells or viral vectors. And many companies are working on “off the shelf” cancer vaccines that aren’t personalized, which would save time and expense. Out of about 400 ongoing clinical trials assessing cancer vaccines last fall, roughly 50 included personalized vaccines.

There’s no guarantee any of these strategies will pan out. Even if they do, success in one type of cancer doesn’t automatically mean success against all. Plenty of cancer therapies have shown enormous promise initially, only to fail when they’re moved into large clinical trials.

But the burst of renewed interest and activity around cancer vaccines is encouraging. And personalized vaccines might have a shot at succeeding where others have failed. The strategy makes sense for “a lot of different tumor types and a lot of different settings,” Brown says. “With this technology, we really have a lot of aspirations.”

Now read the rest of The Checkup

Read more from mit technology review’s archive.

mRNA vaccines transformed the pandemic. But they can do so much more. In this feature from 2023, Jessica Hamzelou covered the myriad other uses of these shots , including fighting cancer. 

This article from 2020 covers some of the background on BioNTech’s efforts to develop personalized cancer vaccines. Adam Piore had the story . 

Years before the pandemic, Emily Mullin wrote about early efforts to develop personalized cancer vaccines—the promise and the pitfalls. 

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• Perspective
• Open access
• Published: 06 May 2024

Leveraging malaria vaccines and mRNA technology to tackle the global inequity in pharmaceutical research and production towards disease elimination

• Floriano Amimo   ORCID: orcid.org/0000-0003-1460-9522 1  

Malaria Journal volume  23 , Article number:  136 ( 2024 ) Cite this article

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Malaria vaccine introduction in endemic countries is a game-changing milestone in the fight against the disease. This article examines the inequity in the global pharmaceutical research, development, manufacturing, and trade landscape. The role of inequity in hindering progress towards malaria elimination is explored. The analysis finds that transformational changes are required to create an equity-enabling environment. Addressing the inequity is critical to maximizing the public health impact of vaccines and attaining sustainability. Avenues to catalyze progress by leveraging malaria vaccines and messenger ribonucleic acid (mRNA) technology are discussed.

The World Health Organization (WHO) recommends childhood malaria immunization with RTS,S/AS01 (RTS,S) and R21/Matrix-M (R21) in endemic countries [ 1 , 2 ]. These pre-erythrocytic virus-like particle vaccines are valuable assets in the fight against malaria with the potential to accelerate progress towards disease elimination, a longstanding global target that has, nevertheless, remained elusive for many African countries. Prior research has shown that 384.7 (uncertainty interval [UI]: 311.7–496.5) cases per 1000, 1.0 (UI: 0.7–1.6) resistant cases per 1000, and 1.1 (UI: 0.8–1.5) deaths per 1000 could be averted with the deployment of a vaccine efficacy of 40% for 10 years [ 3 ].

The introduction of vaccines in endemic countries, therefore, has the potential to revert recent unsatisfactory trends in key indicators, particularly in the context of the coronavirus disease 2019 (COVID-19) pandemic and antimicrobial resistance. Yet inequitable reliance on imported medicines by national malaria control programmes (NMCPs) in Africa may affect the supply, availability, and accessibility of the vaccines and reduce their potential public health impact on the continent.

This article examines the inequity in the global pharmaceutical landscape, from research to trade. It takes an in-depth look at the central but often neglected issues that hamper malaria elimination and eradication while delving into avenues to effectively tackle them. Drawing on current research, it first addresses inequity in essential medicines manufacturing and trade and subsequently examines hindrances to progress in research and development (R&D) in Africa. In each of these two domains, the analysis explores the factors underlying the chronic hurdles and the risks that the resulting inequity poses to the population health and sustainability of NMCPs on the continent. It moreover surveys the challenges facing the policy, strategic, regulatory, and implementation frameworks put in place to address the difficulties. Implications of the recent advances in mRNA-based therapeutics ushered in by the COVID-19 pandemic are explored.

Manufacturing and trade

Reliance on imported medicines has traditionally been a major weakness of malaria control efforts in Africa. About 96–95.4% and 75.7–74.5% of global malaria deaths in 2021–2022 occurred in the WHO African Region (AFR) and among children younger than 5 years (U5) in the region, respectively [ 7 , 12 , 13 ]. Yet the continent has to import medicines to protect itself against the disease. Only 5% and < 1% of the medicines and vaccines Africa consumes and 3% and 0.1–0.2% of the global supply are produced on the continent, respectively [ 9 , 10 , 14 ]. The reliance on imported drugs also affects artemisinin derivatives used for artemisinin-based combination therapy (ACT). These are currently strongly recommended by the WHO as the cornerstone for malaria case management based on high-certainty evidence—artemether-lumefantrine, artesunate-amodiaquine, artesunate-mefloquine, dihydroartemisinin-piperaquine, artesunate-sulfadoxine-pyrimethamine (SP) (ASP)—as well as artesunate-pyronaridine [ 4 ]. Most of these ACT medicines are produced outside the continent, mostly in India [ 5 ] (see Fig.  1 ). This inequitable reliance on imported essential medicines perpetuates the vulnerability of national anti-malarial efforts to disruptions and shocks of global supply chains and systems, as observed at the height of the COVID-19 pandemic. This creates important risks to population health and global health security, thus acting as a structural obstacle to malaria elimination and eradication.

Most artemisinin-based combinations used in malaria-endemic African countries are produced outside the continent. The size of each leftmost and central node and each flow on the left and right side is proportional to the quantity of ACT medicines exported and imported by each producer and consumer country, respectively. The size of each rightmost node represents the quantity of each drug combination shipped. The colour of each left side and right side flow, as well as the leftmost and central nodes, represents each producer and consumer country, respectively. The colour of the rightmost nodes represents each drug combination. Producer and Consumer denote exporter and importer countries or territories represented by ISO 3166-1 alpha-3 codes, respectively. ACT medicines used for artemisinin-based combination therapy, AL artemether-lumefantrine, AP artesunate-pyronaridine, AS-AQ artesunate-amodiaquine, AS-MQ artesunate-mefloquine, ASP artesunate-SP, DHA-PPQ dihydroartemisinin-piperaquine. Data sources: [ 4 , 5 ]

Regional and global efforts to boost local pharmaceutical production (LPP) in Africa have yielded inconsequential results. This is despite the adoption of the Pharmaceutical Manufacturing Plan for Africa (PMPA, aimed at catalyzing LPP to improve public health outcomes) in 2007 and the endorsement of its Business Plan (BP, aimed at providing approaches to accelerate the implementation of the PMPA) in 2012 [ 15 , 16 , 17 ]. Global inequity in drug manufacturing is also being observed with the malaria vaccines. For instance, to date, there are 18 million doses of malaria vaccines available for priority allocation in selected African countries [ 18 ]. How many of these available vaccines were manufactured in an African country? Data shows that all doses of Mosquirix, the trade name of RTS,S, used in Kenya as of 16 September 2023 were imported from Belgium [ 5 ]. This is even though some African countries have some capacity to produce vaccines nationally (Fig.  2 ). This status quo implies that with the expected increase in the supply of malaria vaccines as the cost decreases over time might come further reliance of African countries on imported medical products (MPs).

Geospatial distribution of vaccine production and health financing in Africa. Vaccine production categories shown with surface colour for each country are as follows: Production, countries with active vaccine manufacturing facilities and projects; Project, countries with vaccine manufacturing projects; None, countries without vaccine manufacturing facilities or projects. The colour of each dot is proportional to government health financing measured as the geometric mean of central government health spending as a share of general government expenditure in 2019–2021; the variation in colour intensity between or beyond the two values shown in the legend represents the corresponding variation in government health financing. Most countries do not comply with the Abuja Declaration of 2001 to allocate ≥ 15% of their annual budget to improve the health sector. Investment in vaccine manufacturing without compliance with the Abuja Declaration may result in an important diversion of government funds from the health sector, as suggested by the inverse association between the vaccine production status and government health financing observed in the current analysis (η 2 [H] = 0.17). Data sources: [ 6 , 7 , 8 , 9 , 10 , 11 ]

The COVID-19 pandemic has raised attention to the necessity to produce medicines locally or regionally and even catalyzed processes that could otherwise have taken longer to materialize. Modular mRNA production facilities have been developed by pharmaceutical companies to improve affordability and scale up accessibility of mRNA-based technologies for LPP in low- and middle-income countries (LMICs) [ 19 , 20 ]. The first such a facility (‘‘BioNTainer’’, a platform for mRNA production) was set up in Kigali, Rwanda, in 2023. Just as COVID-19 ushered in the era of mRNA therapeutics and was a catalyst to install some capability for LPP in Africa, the roll-out and introduction of RTS,S and R21 on the continent could thus be leveraged to boost and scale up such LPP capability to meet the demands and accelerate attainment of universal malaria immunization coverage. However, whether, when, or how that will be attained hinges on the solidity and stability of investment in scientific, management, and financing capabilities and practices on the continent (see domain ‘‘Research and development’’). If the hindrances associated with the human component are tackled effectively and sustainably, then these facilities could become an important asset that the continent could leverage to expand its capability to produce sustainably malaria vaccines to reduce the importation and associated public health consequences.

The Framework for Action (FFA) developed by the Partnerships for African Vaccine Manufacturing (PAVM, spearheaded by the Africa Centers for Disease Control and Prevention, established by the African Union (AU) in 2021), approved by the AU in 2022, aims to enable the continent to meet 60% of its vaccine needs through local production by 2040 in the context of AU Agenda 2063 [ 10 ]. Ensuring that the PAVM-FFA does not face the same difficulties that the PMPA (adopted in 2007) and other valuable strategic and higher-level mechanisms and frameworks faced is a major challenge. Current data on the indicators established by the PMPA-BP [ 16 ]—e.g., (i) proportion of pharmaceutical market supplied by African-based manufacturers, (ii) proportion of substandard MPs in the market, (iii) number of companies achieving WHO prequalification, among others—show negligible progress. The reliance on imported medicines continues to date (see data above and Fig.  1 ). The percentage of substandard and falsified (SF) medicines was estimated at 5–40% and 19–50% in several countries on the continent and in the Sahel countries in 2018, respectively [ 21 ]. Furthermore, it was only in 2022 that the first African-based manufacturer, Universal Corporation Limited (Kenya), received WHO prequalification to produce SP [ 22 ]. This is an essential medicine used in the chemoprevention of malaria in pregnancy (intermittent preventive treatment in pregnancy [IPTp]) and childhood (seasonal malaria chemoprevention [SMC] and perennial malaria chemoprevention [PMC]) and as a partner drug for ACT with ASP (also see Fig.  1 ). It can be seen that the PMPA, despite its noble aspirations, has delivered little impact to date.

Major hurdles to these and related mechanisms and frameworks typically reside in their implementation. The rampant epidemics of corruption and mismanagement in most of the continent [ 23 , 24 ] weaken not only public financing of critical infrastructure and services, but also regulatory frameworks, labour productivity, enforcement of rules, and other prerequisites for competitive LPP and trade [ 25 , 26 , 27 , 28 , 29 ]. The placement of unqualified or less qualified professionals in critical positions [ 30 ], a manifestation of these epidemics, lessens the impact of capacity building. Government non-compliance, e.g., with the Abuja Declaration of 2001 [ 6 ] (see Fig.  2 ), also a consequence of mismanagement [ 24 ], compounds the difficulties. These epidemics hinder, e.g., cross-border trade of active pharmaceutical ingredients (APIs) and sustainability of pharmaceutical investments. Thus, corruption and mismanagement are the key barriers to LPP and trade, although the nexus might not always be obvious without a rigorous analysis. Progress tracking is another challenge. An important improvement in PAVM-FFA compared to PMPA-BP is that the former has short-, medium-, and long-term key performance indicator targets [ 10 ], whereas the latter has monitoring and evaluation (M&E) indicators without targets [ 16 ]. However, for both PAVM-FFA and PMPA-BP, no baseline survey was conducted for their indicators, and research funding (e.g., to assess medicine quality) is scanty (see domain ‘‘Research and development’’). As a result, data, e.g., on compliance with pharmacopoeia requirements, is limited on the continent [ 21 ], thereby complicating the M&E of, e.g., the percentage of SF medicines nationally over time. These difficulties are far from new but are typically neglected by efforts aiming to advance LPP and trade in Africa.

Ensuring different outcomes and impacts for PAVM-FFA requires transformation, not simply incremental changes, including in business and governance practices not only across the continent but also in global organizations. A rigorous study of the root causes of chronic non-compliance by AU member states with their regulations and commitments is needed to allow its effective tackling. It is critical to leverage regional, continental, and global initiatives and organizations, e.g., the African Continental Free Trade Area (AfCFTA), World Trade Organization (WTO), United Nations Industrial Development Organization, and WHO, to reduce duplication of efforts, minimize costs, enforce compliance, overcome supply chain barriers, and ensure sustainability. Reform of the international system is necessary to strengthen the capacity of regional, continental, and global organizations to ensure the cost–benefit and sustainability of international investments and strategies to more effectively support LPP and trade in Africa. Doing so could contribute to reducing greatly historical inequities in pharmaceutical manufacturing and trade (as well as R&D). This could allow countries that most need anti-malarial drugs to produce and purchase them locally or regionally and thus remove a major obstacle to malaria elimination and eradication (Fig.  1 ).

In 2022, the WTO temporarily waived the Trade-Related Aspects of Intellectual Property Rights (TRIPS) agreement on MPs for COVID-19, given the exceptional circumstances of the pandemic [ 31 ]. This measure provided a critical facility for the international transfer of knowledge and technology for LPP of MPs for the prevention, diagnosis, and treatment of COVID-19. Given the epidemiological and economic burden of malaria in the AFR [ 12 , 13 , 32 , 33 ], a similar measure could be warranted to boost LPP and accelerate progress towards a world free of malaria. To ensure sustainability and maximize impact, any TRIPS agreement waiver on anti-malarial MPs should be coupled with adequate measures to: (i) incentivize local and international drug innovation and R&D (see domain ‘‘Research and development’’), (ii) strengthen local and continental regulatory, surveillance, and quality assurance capabilities, and (iii) boost continental trade of raw materials and APIs by leveraging the AfCFTA. Making access to TRIPS agreement waivers and similar initiatives conditional on each country’s commitment and progress on these fundamental prerequisites is critical to attaining the transformational changes needed to catalyze advancement in disease control. Failure to do so could complicate the political likelihood or feasibility of a TRIPS agreement waiver for anti-malarial MPs and similar initiatives, e.g., a pandemic treaty.

Transfer of manufacturing plants to endemic countries, an asymmetric initiative, may not on its own be sustainable. African countries need to transform into an environment that disincentivizes corruption and mismanagement. This is a necessary condition to attain a competitive LPP and trade to more effectively combat their major causes of death and suffering, e.g., malaria, towards disease elimination and eradication.

Research and development

What is the contribution of African higher education (HE) institutions to R&D to tackling the continent’s reliance on imported medicines and technology? In most of the continent, HE is not the hub for generating research, knowledge, and innovation but a neglected and underfunded sector, with research itself largely regarded as an appendage, rather than the core, of the academic work stream. Despite the commitment of AU member states in 2007 to allocate ≥ 1% of their gross domestic product in R&D [ 34 ], the continent’s public funding for R&D at 0.42% by 2019 remains one of the poorest, if not the poorest globally, just 25% of the global average of 1.7% [ 35 , 36 ]. Most, if not all, of these countries, including those approved for RTS,S priority allocation, do not comply with the Abuja Declaration of 2001 to allocate ≥ 15% of their annual budget to improve the health sector [ 6 , 37 ]. Among those with a combined share of global malaria mortality in 2021–2022 > 50% [ 12 , 13 ], the average government health financing in 2019–2021 was ≤ 5% in the Democratic Republic of the Congo, the Niger, as well as Tanzania, with little difference in several other countries on the continent (see Fig.  2 ). Rarely can R&D for health take place in such a setting.

These chronic difficulties and failures of governance cannot be tackled without institutional strengthening and eradication of the rampant epidemics of corruption and mismanagement in most of the continent [ 23 , 24 ]. These epidemics are also rampant in HE, affecting, e.g., research fund availability and allocation [ 25 , 38 ]. Successive HE reforms implemented in Africa have failed to solve these and other core issues hindering academic R&D despite gains in other domains [ 39 ]. Poor regulatory frameworks, chronic non-compliance, inconsistent enforcement of rules, and other deficiencies have undermined the realization of the potential of reforms to tackle the root causes of the weaknesses, thereby hampering HE performance. As a result, the global inequity in R&D has lingered. For instance, even after attaining advanced academic qualifications, most African researchers remain stuck in less prominent author list positions in peer-reviewed scientific publications (in the middle) [ 40 ].

Thus, African researchers end up having a limited role in the global research priority-setting, funding allocation, cutting-edge pre-clinical research, new trial designs, setting up of trial networks, and vaccine R&D, thereby weakening the African clinical trial ecosystem [ 41 ] and the scientific productivity and competitiveness of the continent. For instance, promising research by researchers from HE institutions in Australia, New Zealand, and Japan on mRNA malaria vaccine did not involve any African researchers or academic institutions [ 42 ]. In the last 10 years, Africa filed < 1% of global vaccine patents [ 10 ]. This creates a feedback loop, thus perpetuating inequity in pharmaceutical R&D and the reliance on imported medicines and technology. Indeed, even the mRNA clinical trials ongoing in Africa, e.g., for human immunodeficiency virus (HIV, mRNA-1644, Rwanda and South Africa), are typically not spearheaded by African academic, pharmaceutical, or research organizations, but by companies based in higher-income countries [ 43 ].

In the context of chronically limited local R&D, technology importation, that is, transfer, has emerged as an avenue to accelerate tackling inequity. mRNA technology transfer initiatives have been put in motion by development partners to advance R&D in LMICs. These initiatives include the mRNA Technology Transfer Programme established around Afrigen in South Africa in 2021 by the WHO and Medicines Patent Pool to provide technology development, training, and transfer to partners in LMICs [ 44 ]. The Bill & Melinda Gates Foundation has invested or allocated approximately ≥ US$135 million in mRNA research and vaccine manufacturing technology, including $60 million allocated to Quantoom Biosciences (based in Belgium), $5 million to the Institut Pasteur de Dakar (IPD, Senegal), and $5 million to Biovac (South Africa) [ 45 ]. These initiatives are necessary to advance mRNA technology to pave the way for its use to develop medicines for major causes of death and suffering in Africa, such as malaria. They could also contribute to accelerating the reduction of the reliance of African countries on imported medicines. However, the initiatives do not include solutions to address the underlying problems [ 23 , 24 , 38 ] that created the need for technology transfer, such as meager research and innovation in academic institutions in most of the continent. Also, there is an important differential in funding and asymmetry in roles between Europe-based Quantoom Biosciences and Africa-based IPD and Biovac. For instance, Univercells (based in Belgium), a parent company of Quantoom Biosciences, developed a low-cost mRNA research and manufacturing technology that IPD and Biovac are expected to acquire [ 45 ]. This implies that only a part of the funds allocated to African R&D institutes may be used for R&D by them, as the other may have to be ‘‘allocated back’’ to companies from higher-income countries. Thus, these shifts in R&D can deepen inequity rather than tackle it.

Investing in establishing and strengthening research infrastructures and capabilities in HE institutions across Africa similar to those that generated the mRNA technology in higher-income countries could be more impactful and sustainable than simply transferring a mature technology for development and production. An overview of the settings under which the science that led to the mRNA technology emerged and developed can illustrate this. Building on prior work by other researchers since the discovery of deoxyribonucleic acid (DNA) by Johann Friedrich Miescher (University of Tübingen) in 1869 [ 46 ], Watson and Crick (both, University of Cambridge) in the 1950s formulated the current structure of DNA (double helix) [ 47 ]. These researchers made such a contribution working under a solid research infrastructure not dominated by corruption and mismanagement. Such a research infrastructure also allowed expansion and deepening of the understanding of nucleic acids in the subsequent decades. This allowed Karikó and Weissman (both, University of Pennsylvania), since the 1990s, to gradually unlock the therapeutic potential of mRNA—until they finally discovered that using Pseudouridine (Ψ) instead of Uridine (U) could prevent the inflammatory response and increase protein production—thus paving the way for nucleoside-modified mRNA (modRNA) therapeutics [ 48 ]. Even so, a successful mRNA vaccine was not developed until after additional research and funding, including $25 million allocated by the Defense Advanced Research Projects Agency in 2013 to Moderna [ 49 ]. In 2020–2021, as the world was under the COVID-19 global public health emergency, leveraging the accumulated science of nucleic acids, Pfizer/BioNTech and Moderna delivered the first mRNA vaccines [ 50 , 51 ].

It can be seen that the game-changing discoveries that led to the mRNA technology, from Miescher to Karikó and Weissman, took place mostly at universities, which are neglected in most of Africa. Also, it took decades for the results of academic research (nucleic acids) to deliver results with pharmaceutical or clinical applicability (modRNA COVID-19 vaccines). Indeed, even malaria vaccines have been in R&D for at least eight decades. Since at least the 1940s, researchers have been attempting to induce protective immunity to malaria parasites using, e.g., killed or inactivated sporozoites, before RTS,S and R21 (that target the Plasmodium falciparum circumsporozoite protein and, to a lesser extent, the hepatitis B virus surface antigen) became the first and second approved human antiparasitic vaccines in 2021 and 2023, respectively [ 2 , 52 , 53 ]. Thus, substantive funding needs to be allocated continuously to HE institutions for research if game-changing solutions for public health challenges are to be observed on the continent. Sustainability is paramount. Otherwise, if AFR continues to neglect its HE, then even to fight against malaria (a preventable and curable disease whose approximately 3/4 of attributable deaths globally occur in its U5 [ 7 ]) the continent may have to continue relying on imported medicines and technology. Given the complexity of the biology of P. falciparum [ 54 , 55 ], even the mRNA technology transfer, on its own, not coupled with a solid investment in HE on the continent and institutional strengthening, may not be the panacea for meager R&D, at least not as expected.

Creating an R&D infrastructure capable of replicating or surpassing the successes that resulted in the mRNA technology cannot happen under the current academic and research governance and financing systems in Africa. Thus, if the current and future technology transfer or similar initiatives are to tackle the chronic reliance by African countries on imported medicines and technology, they need to invest equally or more in transformational change to address the root causes of the chronic hindrances to progress, not only the consequences. Eradication of the neglected epidemics of corruption and mismanagement on the continent is the most sustainable pathway to accelerate the attainment of equity in pharmaceutical R&D towards malaria elimination and eradication.

Conclusions

Transformation is needed in governance practices throughout the continent and in global organizations, as well as in the pharmaceutical landscape, from research to trade. Tackling inequitable reliance on imported medicines and technology requires solid and stable investment to establish and strengthen research infrastructures and capabilities in academic institutions on the continent. These are a necessary condition to create a sustainable environment capable of enabling endemic countries to boost innovation and LPP. Removing these major structural obstacles in the fight against malaria is critical to ensuring progress in eliminating and eradicating the disease. If these hindrances are tackled effectively and sustainably, the momentum created by malaria vaccine introduction and technological advancements ushered in by the COVID-19 pandemic could be a catalyst for bettering local research, development, and production of medicines. Lessons learned on malaria could then be translated to other vaccine-preventable diseases that, despite having effective vaccines, continue to burden the continent.

Availability of data and materials

The datasets used in the current study are publicly available and can be efficiently extracted from the sources cited in the article. The processed data that were presented in the main text and/or used to draw the graphs are available from the corresponding author upon reasonable request. The data analysis was performed using R version 4.3.0. Data and code sharing will require a Materials Transfer Agreement (MTA).

Abbreviations

Artemisinin-based combination therapy

African Continental Free Trade Area

WHO African Region

Active pharmaceutical ingredient

Artesunate-SP

African Union

Business plan

Coronavirus disease 2019

Deoxyribonucleic acid

Framework for action

Higher education

Institut Pasteur de Dakar

Low- and middle-income country

Local pharmaceutical production

Monitoring and evaluation

Nucleoside-modified mRNA

Medical product

Messenger ribonucleic acid

National Malaria Control Programme

Partnerships for African Vaccine Manufacturing

Pharmaceutical Manufacturing Plan for Africa

• R21/Matrix-M

Substandard and falsified

Sulfadoxine-pyrimethamine

Trade-Related Aspects of Intellectual Property Rights

Children younger than 5 years

Uncertainty interval

World Health Organization

World Trade Organization

WHO. Malaria vaccine: WHO position paper – March 2022. Wkly Epidemiol Rec. 2022;97:60–78.

World Health Organization. WHO recommends R21/Matrix-M vaccine for malaria prevention in updated advice on immunization. Geneva: World Health Organization; 2023.

Google Scholar  

Hamilton A, Haghpanah F, Hasso-Agopsowicz M, Frost I, Lin G, Schueller E, et al. Modeling of malaria vaccine effectiveness on disease burden and drug resistance in 42 African countries. Commun Med (Lond). 2023;3:144.

Article   PubMed   PubMed Central   Google Scholar  

World Health Organization. WHO guidelines for malaria. Geneva: World Health Organization; 2023.

Volza. Global export import trade data of 209+ countries. Rehoboth BCH: Volza; 2023.

Organisation of African Unity. Abuja declaration on HIV/AIDS, tuberculosis and other related infectious diseases. Abuja; 2001.

Amimo F. Malaria vaccination: hurdles to reach high-risk children. BMC Med. 2024;22:111.

Georgieva K. Support for Africa’s vaccine production is good for the world: robust and reliable vaccine capacity in Africa is a global public good, deserving of global support. Washington: International Monetary Fund; 2022.

Gavi, The Vaccine Alliance. Expanding sustainable vaccine manufacturing in Africa: priorities for support. Geneva: Gavi, the Vaccine Alliance; 2022.

Africa Centres for Disease Control and Prevention. Partnerships for African Vaccine Manufacturing (PAVM) Framework for Action. Addis Ababa: Africa Centres for Disease Control and Prevention; 2022.

WHO. What is Africa’s vaccine production capacity? Brazzaville: World Health Organization Regional Office for Africa; 2021.

WHO. World malaria report 2022. Geneva: World Health Organization; 2022.

WHO. World malaria report 2023. Geneva: World Health Organization; 2023.

WHO. Inside Africa’s drive to boost medicines and vaccine manufacturing. Addis Ababa: World Health Organization – Ethiopia; 2021.

African Union. Pharmaceutical manufacturing plan for Africa. Addis Ababa; 2007.

African Union Commission (AUC) – United Nations Industrial Development Organization (UNIDO). Pharmaceutical manufacturing plan for Africa business plan. Addis Ababa: African Union; 2012.

Byaruhanga J. The pharmaceutical manufacturing plan for Africa. Midrand: African Union Development Agency-New Partnership for Africa’s Development (AUDA-NEPAD); 2020.

WHO. First malaria vaccine supply allocations May 2023: explanation of process and outcomes. Geneva: World Health Organization; 2023.

BioNTech. BioNTech achieves milestone at mRNA-based vaccine manufacturing site in Rwanda. Mainz: BioNTech; 2023.

Quantoom Biosciences. Etherna Immunotherapies and Quantoom Biosciences announce a strategic collaboration for the development of a novel RNA production system. Niel and Brussels: Quantoom Biosciences; 2021.

United Nations Office on Drugs and Crime. Trafficking in medical products in the Sahel: transnational organized crime threat assessment – Sahel. Vienna: United Nations Office on Drugs and Crime; 2023.

Book   Google Scholar  

Medicines for Malaria Venture. First African-manufactured medicine to prevent malaria in pregnant women and infants quality-approved by WHO. Geneva: MMV; 2022.

Transparency International. Corruption perceptions index 2023. Berlin: Transparency International; 2024.

Adeboye T, Economic and Social Council; United Nations, Economic Commission For Africa. Underdevelopment and natural resource abundance in Africa. ECA meeting of the Committee on Natural Resources and Science and Technology. Addis Ababa; 1999.

African Union. Stolen futures: the impact of corruption on children in Africa. Addis Ababa; 2021.

Griffore KA, Bowra A, Guilcher SJT, Kohler J. Corruption risks in health procurement during the COVID-19 pandemic and anti-corruption, transparency and accountability (ACTA) mechanisms to reduce these risks: a rapid review. Global Health. 2023;19:91.

Kohler JC, Martinez MG, Petrov M, Sale J. Corruption in the pharmaceutical sector: diagnosing the challenges. London: Transparency International UK; 2016. https://www.transparency.org.uk/sites/default/files/pdf/publications/29-06-2016-Corruption_In_The_Pharmaceutical_Sector_Web-2.pdf

Sié KJF. Industrial policy and labour productivity growth in Africa: does the technology choice matter? J Econ Struct. 2023;12:10.

Article   Google Scholar  

De Rosa D, Gooroochurn N, Görg H. Corruption and productivity: firm-level evidence. Jahrb Natl Okon Stat. 2015;235:115–38.

The Africa Report. AU: member states complain of unfair hiring practices, internal corruption. Paris; 2023.

World Trade Organization. Ministerial decision on the TRIPS agreement. Geneva; 2022.

Andrade MV, Noronha K, Diniz BPC, Guedes G, Carvalho LR, Silva VA, et al. The economic burden of malaria: a systematic review. Malar J. 2022;21:283.

Cirera L, Sacoor C, Meremikwu M, Ranaivo L, Manun’Ebo M, Arikpo D, et al. The economic costs of malaria in pregnancy: evidence from four sub-Saharan countries. Gates Open Res. 2023;7:47.

African Union. Assembly of the African Union eighth ordinary session: decisions and declarations. Addis Ababa; 2007.

Caelers D, Okoth D. Research funding in Africa: navigating sustainability and shifting perspectives. Nat Africa. 2023. https://doi.org/10.1038/d44148-023-00360-4 .

Adepoju P. Africa’s future depends on government-funded R&D: investing in research is key pathway to development on the continent. Nat Africa. 2022. https://doi.org/10.1038/d44148-022-00134-4 .

Kurowski C, Kumar A, Mieses Ramirez JC, Schmidt M, Silfverberg DV. Health financing in a time of global shocks: strong advance, early retreat. Washington: The International Bank for Reconstruction and Development/The World Bank; 2023.

Ngcamu BS, Mantzaris E. Anatomy and the detection of corruption in ‘previously disadvantaged’ South African universities. J Contemp Manage. 2023;20:323–49.

Varghese N. Governance reforms in higher education: a study of selected countries in Africa. Paris: United Nations Educational, Scientific and Cultural Organization (UNESCO) - International Institute for Educational Planning (IIEP); 2016.

Hedt-Gauthier BL, Jeufack HM, Neufeld NH, Alem A, Sauer S, Odhiambo J, et al. Stuck in the middle: a systematic review of authorship in collaborative health research in Africa, 2014–2016. BMJ Glob Health. 2019;4:e001853.

Africa Centers for Disease Control and Prevention (Africa CDC) – African Union Development Agency-New Partnership for Africa’s Development (AUDA-NEPAD). Optimizing efficiency and impact in the African clinical trials ecosystem. Addis Ababa: Africa Centers for Disease Control and Prevention (Africa CDC) – African Union Development Agency-New Partnership for Africa’s Development (AUDA-NEPAD); 2023.

Ganley M, Holz LE, Minnell JJ, de Menezes MN, Burn OK, Yew Poa KC, et al. mRNA vaccine against malaria tailored for liver-resident memory T cells. Nat Immunol. 2023;24:1487–98.

Article   CAS   PubMed   Google Scholar  

Saied AA. Building Africa’s first mRNA vaccine facility. Lancet. 2023;402:287–8.

Article   PubMed   Google Scholar  

WHO. mRNA Technology Transfer Programme moves to the next phase of its development. Geneva: World Health Organization; 2023.

Bill & Melinda Gates Foundation. Gates Foundation to accelerate mRNA vaccine innovation and manufacturing in Africa and globally. Seattle: Bill & Melinda Gates Foundation; 2023.

Dahm R. Discovering DNA: Friedrich Miescher and the early years of nucleic acid research. Hum Genet. 2008;122:565–81.

Watson JD, Crick FH. Molecular structure of nucleic acids: a structure for deoxyribose nucleic acid. Nature. 1953;171:737–8.

The Nobel Assembly at The Karolinska Institutet. Scientific background 2023 – Discoveries concerning nucleoside base modifications that enabled the development of effective mRNA vaccines against COVID-19. Stockholm; 2023.

The Economist. A growing number of governments hope to clone America’s DARPA. London; 2021.

World Health Organization. WHO issues its first emergency use validation for a COVID-19 vaccine and emphasizes need for equitable global access. Geneva: World Health Organization; 2020.

WHO. Recommendation for an emergency use listing of COVID-19 mRNA vaccine (nucleoside modified) submitted by Moderna Biotech (Spain). Geneva: World Health Organization; 2021.

El-Moamly AA, El-Sweify MA. Malaria vaccines: the 60-year journey of hope and final success—lessons learned and future prospects. Trop Med Health. 2023;51:29.

Nussenzweig RS, Vanderberg J, Most H, Orton C. Protective immunity produced by the injection of x-irradiated sporozoites of Plasmodium berghei . Nature. 1967;216:160–2.

Anton L, Cobb DW, Ho CM. Structural parasitology of the malaria parasite Plasmodium falciparum . Trends Biochem Sci. 2022;47:149–59.

Oyedeji SI, Bassi PU, Oyedeji SA, Ojurongbr O, Oluwatoyin H. Genetic diversity and complexity of Plasmodium falciparum infections in the microenvironment among siblings of the same household in North-Central Nigeria. Malar J. 2020;19:338.

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Amimo, F. Leveraging malaria vaccines and mRNA technology to tackle the global inequity in pharmaceutical research and production towards disease elimination. Malar J 23 , 136 (2024). https://doi.org/10.1186/s12936-024-04972-5

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• Review Article
• Published: 12 January 2018

mRNA vaccines — a new era in vaccinology

• Norbert Pardi 1 ,
• Michael J. Hogan 1 ,
• Frederick W. Porter 2 &
• Drew Weissman 1  

Nature Reviews Drug Discovery volume  17 ,  pages 261–279 ( 2018 ) Cite this article

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• Drug discovery
• Infectious diseases
• RNA vaccines

Recent improvements in mRNA vaccines act to increase protein translation, modulate innate and adaptive immunogenicity and improve delivery.

mRNA vaccines have elicited potent immunity against infectious disease targets in animal models of influenza virus, Zika virus, rabies virus and others, especially in recent years, using lipid-encapsulated or naked forms of sequence-optimized mRNA.

Diverse approaches to mRNA cancer vaccines, including dendritic cell vaccines and various types of directly injectable mRNA, have been employed in numerous cancer clinical trials, with some promising results showing antigen-specific T cell responses and prolonged disease-free survival in some cases.

Therapeutic considerations and challenges include scaling up good manufacturing practice (GMP) production, establishing regulations, further documenting safety and increasing efficacy.

Important future directions of research will be to compare and elucidate the immune pathways activated by various mRNA vaccine platforms, to improve current approaches based on these mechanisms and to initiate new clinical trials against additional disease targets.

mRNA vaccines represent a promising alternative to conventional vaccine approaches because of their high potency, capacity for rapid development and potential for low-cost manufacture and safe administration. However, their application has until recently been restricted by the instability and inefficient in vivo delivery of mRNA. Recent technological advances have now largely overcome these issues, and multiple mRNA vaccine platforms against infectious diseases and several types of cancer have demonstrated encouraging results in both animal models and humans. This Review provides a detailed overview of mRNA vaccines and considers future directions and challenges in advancing this promising vaccine platform to widespread therapeutic use.

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Exploring the reported adverse effects of COVID-19 vaccines among vaccinated Arab populations: a multi-national survey study

A guide to vaccinology: from basic principles to new developments

Lipid nanoparticles for mRNA delivery

Vaccines prevent many millions of illnesses and save numerous lives every year 1 . As a result of widespread vaccine use, the smallpox virus has been completely eradicated and the incidence of polio, measles and other childhood diseases has been drastically reduced around the world 2 . Conventional vaccine approaches, such as live attenuated and inactivated pathogens and subunit vaccines, provide durable protection against a variety of dangerous diseases 3 . Despite this success, there remain major hurdles to vaccine development against a variety of infectious pathogens, especially those better able to evade the adaptive immune response 4 . Moreover, for most emerging virus vaccines, the main obstacle is not the effectiveness of conventional approaches but the need for more rapid development and large-scale deployment. Finally, conventional vaccine approaches may not be applicable to non-infectious diseases, such as cancer. The development of more potent and versatile vaccine platforms is therefore urgently needed.

Nucleic acid therapeutics have emerged as promising alternatives to conventional vaccine approaches. The first report of the successful use of in vitro transcribed (IVT) mRNA in animals was published in 1990, when reporter gene mRNAs were injected into mice and protein production was detected 5 . A subsequent study in 1992 demonstrated that administration of vasopressin-encoding mRNA in the hypothalamus could elicit a physiological response in rats 6 . However, these early promising results did not lead to substantial investment in developing mRNA therapeutics, largely owing to concerns associated with mRNA instability, high innate immunogenicity and inefficient in vivo delivery. Instead, the field pursued DNA-based and protein-based therapeutic approaches 7 , 8 .

Over the past decade, major technological innovation and research investment have enabled mRNA to become a promising therapeutic tool in the fields of vaccine development and protein replacement therapy. The use of mRNA has several beneficial features over subunit, killed and live attenuated virus, as well as DNA-based vaccines. First, safety: as mRNA is a non-infectious, non-integrating platform, there is no potential risk of infection or insertional mutagenesis. Additionally, mRNA is degraded by normal cellular processes, and its in vivo half-life can be regulated through the use of various modifications and delivery methods 9 , 10 , 11 , 12 . The inherent immunogenicity of the mRNA can be down-modulated to further increase the safety profile 9 , 12 , 13 . Second, efficacy: various modifications make mRNA more stable and highly translatable 9 , 12 , 13 . Efficient in vivo delivery can be achieved by formulating mRNA into carrier molecules, allowing rapid uptake and expression in the cytoplasm (reviewed in Refs 10 , 11 ). mRNA is the minimal genetic vector; therefore, anti-vector immunity is avoided, and mRNA vaccines can be administered repeatedly. Third, production: mRNA vaccines have the potential for rapid, inexpensive and scalable manufacturing, mainly owing to the high yields of in vitro transcription reactions.

The mRNA vaccine field is developing extremely rapidly; a large body of preclinical data has accumulated over the past several years, and multiple human clinical trials have been initiated. In this Review, we discuss current mRNA vaccine approaches, summarize the latest findings, highlight challenges and recent successes, and offer perspectives on the future of mRNA vaccines. The data suggest that mRNA vaccines have the potential to solve many of the challenges in vaccine development for both infectious diseases and cancer.

Basic mRNA vaccine pharmacology

mRNA is the intermediate step between the translation of protein-encoding DNA and the production of proteins by ribosomes in the cytoplasm. Two major types of RNA are currently studied as vaccines: non-replicating mRNA and virally derived, self-amplifying RNA. Conventional mRNA-based vaccines encode the antigen of interest and contain 5′ and 3′ untranslated regions (UTRs), whereas self-amplifying RNAs encode not only the antigen but also the viral replication machinery that enables intracellular RNA amplification and abundant protein expression.

The construction of optimally translated IVT mRNA suitable for therapeutic use has been reviewed previously 14 , 15 . Briefly, IVT mRNA is produced from a linear DNA template using a T7, a T3 or an Sp6 phage RNA polymerase 16 . The resulting product should optimally contain an open reading frame that encodes the protein of interest, flanking UTRs, a 5′ cap and a poly(A) tail. The mRNA is thus engineered to resemble fully processed mature mRNA molecules as they occur naturally in the cytoplasm of eukaryotic cells.

Complexing of mRNA for in vivo delivery has also been recently detailed 10 , 11 . Naked mRNA is quickly degraded by extracellular RNases 17 and is not internalized efficiently. Thus, a great variety of in vitro and in vivo transfection reagents have been developed that facilitate cellular uptake of mRNA and protect it from degradation. Once the mRNA transits to the cytosol, the cellular translation machinery produces protein that undergoes post-translational modifications, resulting in a properly folded, fully functional protein. This feature of mRNA pharmacology is particularly advantageous for vaccines and protein replacement therapies that require cytosolic or transmembrane proteins to be delivered to the correct cellular compartments for proper presentation or function. IVT mRNA is finally degraded by normal physiological processes, thus reducing the risk of metabolite toxicity.

Recent advances in mRNA vaccine technology

Various mRNA vaccine platforms have been developed in recent years and validated in studies of immunogenicity and efficacy 18 , 19 , 20 . Engineering of the RNA sequence has rendered synthetic mRNA more translatable than ever before. Highly efficient and non-toxic RNA carriers have been developed that in some cases 21 , 22 allow prolonged antigen expression in vivo ( Table 1 ). Some vaccine formulations contain novel adjuvants, while others elicit potent responses in the absence of known adjuvants. The following section summarizes the key advances in these areas of mRNA engineering and their impact on vaccine efficacy.

Optimization of mRNA translation and stability

This topic has been extensively discussed in previous reviews 14 , 15 ; thus, we briefly summarize the key findings ( Box 1 ). The 5′ and 3′ UTR elements flanking the coding sequence profoundly influence the stability and translation of mRNA, both of which are critical concerns for vaccines. These regulatory sequences can be derived from viral or eukaryotic genes and greatly increase the half-life and expression of therapeutic mRNAs 23 , 24 . A 5′ cap structure is required for efficient protein production from mRNA 25 . Various versions of 5′ caps can be added during or after the transcription reaction using a vaccinia virus capping enzyme 26 or by incorporating synthetic cap or anti-reverse cap analogues 27 , 28 . The poly(A) tail also plays an important regulatory role in mRNA translation and stability 25 ; thus, an optimal length of poly(A) 24 must be added to mRNA either directly from the encoding DNA template or by using poly(A) polymerase. The codon usage additionally has an impact on protein translation. Replacing rare codons with frequently used synonymous codons that have abundant cognate tRNA in the cytosol is a common practice to increase protein production from mRNA 29 , although the accuracy of this model has been questioned 30 . Enrichment of G:C content constitutes another form of sequence optimization that has been shown to increase steady-state mRNA levels in vitro 31 and protein expression in vivo 12 .

Although protein expression may be positively modulated by altering the codon composition or by introducing modified nucleosides (discussed below), it is also possible that these forms of sequence engineering could affect mRNA secondary structure 32 , the kinetics and accuracy of translation and simultaneous protein folding 33 , 34 , and the expression of cryptic T cell epitopes present in alternative reading frames 30 . All these factors could potentially influence the magnitude or specificity of the immune response.

Box 1: Strategies for optimizing mRNA pharmacology

A number of technologies are currently used to improve the pharmacological aspects of mRNA. The various mRNA modifications used and their impact are summarized below.

• Synthetic cap analogues and capping enzymes 26 , 27 stabilize mRNA and increase protein translation via binding to eukaryotic translation initiation factor 4E (EIF4E)

• Regulatory elements in the 5′-untranslated region (UTR) and the 3′-UTR 23 stabilize mRNA and increase protein translation

• Poly(A) tail 25 stabilizes mRNA and increases protein translation

• Modified nucleosides 9 , 48 decrease innate immune activation and increase translation

• Separation and/or purification techniques: RNase III treatment (N.P. and D.W., unpublished observations) and fast protein liquid chromatography (FPLC) purification 13 decrease immune activation and increase translation

• Sequence and/or codon optimization 29 increase translation

• Modulation of target cells: co-delivery of translation initiation factors and other methods alters translation and immunogenicity

Modulation of immunogenicity

Exogenous mRNA is inherently immunostimulatory, as it is recognized by a variety of cell surface, endosomal and cytosolic innate immune receptors ( Fig. 1 ) (reviewed in Ref. 35 ). Depending on the therapeutic application, this feature of mRNA could be beneficial or detrimental. It is potentially advantageous for vaccination because in some cases it may provide adjuvant activity to drive dendritic cell (DC) maturation and thus elicit robust T and B cell immune responses. However, innate immune sensing of mRNA has also been associated with the inhibition of antigen expression and may negatively affect the immune response 9 , 13 . Although the paradoxical effects of innate immune sensing on different formats of mRNA vaccines are incompletely understood, some progress has been made in recent years in elucidating these phenomena.

Innate immune sensing of two types of mRNA vaccine by a dendritic cell (DC), with RNA sensors shown in yellow, antigen in red, DC maturation factors in green, and peptide−major histocompatibility complex (MHC) complexes in light blue and red; an example lipid nanoparticle carrier is shown at the top right. A non-exhaustive list of the major known RNA sensors that contribute to the recognition of double-stranded and unmodified single-stranded RNAs is shown. Unmodified, unpurified (part a ) and nucleoside-modified, fast protein liquid chromatography (FPLC)-purified (part b ) mRNAs were selected for illustration of two formats of mRNA vaccines where known forms of mRNA sensing are present and absent, respectively. The dashed arrow represents reduced antigen expression. Ag, antigen; PKR, interferon-induced, double-stranded RNA-activated protein kinase; MDA5, interferon-induced helicase C domain-containing protein 1 (also known as IFIH1); IFN, interferon; m1Ψ, 1-methylpseudouridine; OAS, 2′-5′-oligoadenylate synthetase; TLR, Toll-like receptor.

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Studies over the past decade have shown that the immunostimulatory profile of mRNA can be shaped by the purification of IVT mRNA and the introduction of modified nucleosides as well as by complexing the mRNA with various carrier molecules 9 , 13 , 36 , 37 . Enzymatically synthesized mRNA preparations contain double-stranded RNA (dsRNA) contaminants as aberrant products of the IVT reaction 13 . As a mimic of viral genomes and replication intermediates, dsRNA is a potent pathogen-associated molecular pattern (PAMP) that is sensed by pattern recognition receptors in multiple cellular compartments ( Fig. 1 ). Recognition of IVT mRNA contaminated with dsRNA results in robust type I interferon production 13 , which upregulates the expression and activation of protein kinase R (PKR; also known as EIF2AK2) and 2′-5′-oligoadenylate synthetase (OAS), leading to the inhibition of translation 38 and the degradation of cellular mRNA and ribosomal RNA 39 , respectively. Karikó and colleagues 13 have demonstrated that contaminating dsRNA can be efficiently removed from IVT mRNA by chromatographic methods such as reverse-phase fast protein liquid chromatography (FPLC) or high-performance liquid chromatography (HPLC). Strikingly, purification by FPLC has been shown to increase protein production from IVT mRNA by up to 1,000-fold in primary human DCs 13 . Thus, appropriate purification of IVT mRNA seems to be critical for maximizing protein (immunogen) production in DCs and for avoiding unwanted innate immune activation.

Besides dsRNA contaminants, single-stranded mRNA molecules are themselves a PAMP when delivered to cells exogenously. Single-stranded oligoribonucleotides and their degradative products are detected by the endosomal sensors Toll-like receptor 7 (TLR7) and TLR8 (Refs 40 , 41 ), resulting in type I interferon production 42 . Crucially, it was discovered that the incorporation of naturally occurring chemically modified nucleosides, including but not limited to pseudouridine 9 , 43 , 44 and 1-methylpseudouridine 45 , prevents activation of TLR7, TLR8 and other innate immune sensors 46 , 47 , thus reducing type I interferon signalling 48 . Nucleoside modification also partially suppresses the recognition of dsRNA species 46 , 47 , 48 . As a result, Karikó and others have shown that nucleoside-modified mRNA is translated more efficiently than unmodified mRNA in vitro 9 , particularly in primary DCs, and in vivo in mice 45 . Notably, the highest level of protein production in DCs was observed when mRNA was both FPLC-purified and nucleoside-modified 13 . These advances in understanding the sources of innate immune sensing and how to avoid their adverse effects have substantially contributed to the current interest in mRNA-based vaccines and protein replacement therapies.

In contrast to the findings described above, a study by Thess and colleagues found that sequence-optimized, HPLC-purified, unmodified mRNA produced higher levels of protein in HeLa cells and in mice than its nucleoside-modified counterpart 12 . Additionally, Kauffman and co-workers demonstrated that unmodified, non-HPLC-purified mRNA yielded more robust protein production in HeLa cells than nucleoside-modified mRNA, and resulted in similar levels of protein production in mice 49 . Although not fully clear, the discrepancies between the findings of Karikó 9 , 13 and these authors 12 , 49 may have arisen from variations in RNA sequence optimization, the stringency of mRNA purification to remove dsRNA contaminants and the level of innate immune sensing in the targeted cell types.

The immunostimulatory properties of mRNA can conversely be increased by the inclusion of an adjuvant to increase the potency of some mRNA vaccine formats. These include traditional adjuvants as well as novel approaches that take advantage of the intrinsic immunogenicity of mRNA or its ability to encode immune-modulatory proteins. Self-replicating RNA vaccines have displayed increased immunogenicity and effectiveness after formulating the RNA in a cationic nanoemulsion based on the licensed MF59 (Novartis) adjuvant 50 . Another effective adjuvant strategy is TriMix, a combination of mRNAs encoding three immune activator proteins: CD70, CD40 ligand (CD40L) and constitutively active TLR4. TriMix mRNA augmented the immunogenicity of naked, unmodified, unpurified mRNA in multiple cancer vaccine studies and was particularly associated with increased DC maturation and cytotoxic T lymphocyte (CTL) responses (reviewed in Ref. 51 ). The type of mRNA carrier and the size of the mRNA–carrier complex have also been shown to modulate the cytokine profile induced by mRNA delivery. For example, the RNActive (CureVac AG) vaccine platform 52 , 53 depends on its carrier to provide adjuvant activity. In this case, the antigen is expressed from a naked, unmodified, sequence-optimized mRNA, while the adjuvant activity is provided by co-delivered RNA complexed with protamine (a polycationic peptide), which acts via TLR7 signalling 52 , 54 . This vaccine format has elicited favourable immune responses in multiple preclinical animal studies for vaccination against cancer and infectious diseases 18 , 36 , 55 , 56 . A recent study provided mechanistic information on the adjuvanticity of RNActive vaccines in mice in vivo and human cells in vitro 54 . Potent activation of TLR7 (mouse and human) and TLR8 (human) and production of type I interferon, pro-inflammatory cytokines and chemokines after intradermal immunization was shown 54 . A similar adjuvant activity was also demonstrated in the context of non-mRNA-based vaccines using RNAdjuvant (CureVac AG), an unmodified, single-stranded RNA stabilized by a cationic carrier peptide 57 .

Progress in mRNA vaccine delivery

Efficient in vivo mRNA delivery is critical to achieving therapeutic relevance. Exogenous mRNA must penetrate the barrier of the lipid membrane in order to reach the cytoplasm to be translated to functional protein. mRNA uptake mechanisms seem to be cell type dependent, and the physicochemical properties of the mRNA complexes can profoundly influence cellular delivery and organ distribution. There are two basic approaches for the delivery of mRNA vaccines that have been described to date. First, loading of mRNA into DCs ex vivo , followed by re-infusion of the transfected cells 58 ; and second, direct parenteral injection of mRNA with or without a carrier. Ex vivo DC loading allows precise control of the cellular target, transfection efficiency and other cellular conditions, but as a form of cell therapy, it is an expensive and labour-intensive approach to vaccination. Direct injection of mRNA is comparatively rapid and cost-effective, but it does not yet allow precise and efficient cell-type-specific delivery, although there has been recent progress in this regard 59 . Both of these approaches have been explored in a variety of forms ( Fig. 2 ; Table 1 ).

Commonly used delivery methods and carrier molecules for mRNA vaccines along with typical diameters for particulate complexes are shown: naked mRNA (part a ); naked mRNA with in vivo electroporation (part b ); protamine (cationic peptide)-complexed mRNA (part c ); mRNA associated with a positively charged oil-in-water cationic nanoemulsion (part d ); mRNA associated with a chemically modified dendrimer and complexed with polyethylene glycol (PEG)-lipid (part e ); protamine-complexed mRNA in a PEG-lipid nanoparticle (part f ); mRNA associated with a cationic polymer such as polyethylenimine (PEI) (part g ); mRNA associated with a cationic polymer such as PEI and a lipid component (part h ); mRNA associated with a polysaccharide (for example, chitosan) particle or gel (part i ); mRNA in a cationic lipid nanoparticle (for example, 1,2-dioleoyloxy-3-trimethylammoniumpropane (DOTAP) or dioleoylphosphatidylethanolamine (DOPE) lipids) (part j ); mRNA complexed with cationic lipids and cholesterol (part k ); and mRNA complexed with cationic lipids, cholesterol and PEG-lipid (part l ).

Ex vivo loading of DCs. DCs are the most potent antigen-presenting cells of the immune system. They initiate the adaptive immune response by internalizing and proteolytically processing antigens and presenting them to CD8 + and CD4 + T cells on major histocompatibility complexes (MHCs), namely, MHC class I and MHC class II , respectively. Additionally, DCs may present intact antigen to B cells to provoke an antibody response 60 . DCs are also highly amenable to mRNA transfection. For these reasons, DCs represent an attractive target for transfection by mRNA vaccines, both in vivo and ex vivo .

Although DCs have been shown to internalize naked mRNA through a variety of endocytic pathways 61 , 62 , 63 , ex vivo transfection efficiency is commonly increased using electroporation; in this case, mRNA molecules pass through membrane pores formed by a high-voltage pulse and directly enter the cytoplasm (reviewed in Ref. 64 ). This mRNA delivery approach has been favoured for its ability to generate high transfection efficiency without the need for a carrier molecule. DCs that are loaded with mRNA ex vivo are then re-infused into the autologous vaccine recipient to initiate the immune response. Most ex vivo -loaded DC vaccines elicit a predominantly cell-mediated immune response; thus, they have been used primarily to treat cancer (reviewed in Ref. 58 ).

Injection of naked mRNA in vivo. Naked mRNA has been used successfully for in vivo immunizations, particularly in formats that preferentially target antigen-presenting cells, as in intradermal 61 , 65 and intranodal injections 66 , 67 , 68 . Notably, a recent report showed that repeated intranodal immunizations with naked, unmodified mRNA encoding tumour-associated neoantigens generated robust T cell responses and increased progression-free survival 68 (discussed further in Box 2 ).

Physical delivery methods in vivo. To increase the efficiency of mRNA uptake in vivo , physical methods have occasionally been used to penetrate the cell membrane. An early report showed that mRNA complexed with gold particles could be expressed in tissues using a gene gun, a microprojectile method 69 . The gene gun was shown to be an efficient RNA delivery and vaccination method in mouse models 70 , 71 , 72 , 73 , but no efficacy data in large animals or humans are available. In vivo electroporation has also been used to increase uptake of therapeutic RNA 74 , 75 , 76 ; however, in one study, electroporation increased the immunogenicity of only a self-amplifying RNA and not a non-replicating mRNA-based vaccine 74 . Physical methods can be limited by increased cell death and restricted access to target cells or tissues. Recently, the field has instead favoured the use of lipid or polymer-based nanoparticles as potent and versatile delivery vehicles.

Protamine. The cationic peptide protamine has been shown to protect mRNA from degradation by serum RNases 77 ; however, protamine-complexed mRNA alone demonstrated limited protein expression and efficacy in a cancer vaccine model, possibly owing to an overly tight association between protamine and mRNA 36 , 78 . This issue was resolved by developing the RNActive vaccine platform, in which protamine-formulated RNA serves only as an immune activator and not as an expression vector 52 .

Cationic lipid and polymer-based delivery. Highly efficient mRNA transfection reagents based on cationic lipids or polymers, such as TransIT-mRNA (Mirus Bio LLC) or Lipofectamine (Invitrogen), are commercially available and work well in many primary cells and cancer cell lines 9 , 13 , but they often show limited in vivo efficacy or a high level of toxicity (N.P. and D.W., unpublished observations). Great progress has been made in developing similarly designed complexing reagents for safe and effective in vivo use, and these are discussed in detail in several recent reviews 10 , 11 , 79 , 80 . Cationic lipids and polymers, including dendrimers, have become widely used tools for mRNA administration in the past few years. The mRNA field has clearly benefited from the substantial investment in in vivo small interfering RNA (siRNA) administration, where these delivery vehicles have been used for over a decade. Lipid nanoparticles (LNPs) have become one of the most appealing and commonly used mRNA delivery tools. LNPs often consist of four components: an ionizable cationic lipid, which promotes self-assembly into virus-sized (~100 nm) particles and allows endosomal release of mRNA to the cytoplasm; lipid-linked polyethylene glycol (PEG), which increases the half-life of formulations; cholesterol, a stabilizing agent; and naturally occurring phospholipids, which support lipid bilayer structure. Numerous studies have demonstrated efficient in vivo siRNA delivery by LNPs (reviewed in Ref. 81 ), but it has only recently been shown that LNPs are potent tools for in vivo delivery of self-amplifying RNA 19 and conventional, non-replicating mRNA 21 . Systemically delivered mRNA–LNP complexes mainly target the liver owing to binding of apolipoprotein E and subsequent receptor-mediated uptake by hepatocytes 82 , and intradermal, intramuscular and subcutaneous administration have been shown to produce prolonged protein expression at the site of the injection 21 , 22 . The mechanisms of mRNA escape into the cytoplasm are incompletely understood, not only for artificial liposomes but also for naturally occurring exosomes 83 . Further research into this area will likely be of great benefit to the field of therapeutic RNA delivery.

The magnitude and duration of in vivo protein production from mRNA–LNP vaccines can be controlled in part by varying the route of administration. Intramuscular and intradermal delivery of mRNA–LNPs has been shown to result in more persistent protein expression than systemic delivery routes: in one experiment, the half-life of mRNA-encoded firefly luciferase was roughly threefold longer after intradermal injection than after intravenous delivery 21 . These kinetics of mRNA–LNP expression may be favourable for inducing immune responses. A recent study demonstrated that sustained antigen availability during vaccination was a driver of high antibody titres and germinal centre (GC) B cell and T follicular helper (T FH ) cell responses 84 . This process was potentially a contributing factor to the potency of recently described nucleoside-modified mRNA–LNP vaccines delivered by the intramuscular and intradermal routes 20 , 22 , 85 . Indeed, T FH cells have been identified as a critical population of immune cells that vaccines must activate in order to generate potent and long-lived neutralizing antibody responses, particularly against viruses that evade humoral immunity 86 . The dynamics of the GC reaction and the differentiation of T FH cells are incompletely understood, and progress in these areas would undoubtedly be fruitful for future vaccine design ( Box 3 ).

Box 2: Personalized neoepitope cancer vaccines

Sahin and colleagues have pioneered the use of individualized neoepitope mRNA cancer vaccines 121 . They use high-throughput sequencing to identify every unique somatic mutation of an individual patient's tumour sample, termed the mutanome. This enables the rational design of neoepitope cancer vaccines in a patient-specific manner, and has the advantage of targeting non-self antigen specificities that should not be eliminated by central tolerance mechanisms. Proof of concept has been recently provided: Kreiter and colleagues found that a substantial portion of non-synonymous cancer mutations were immunogenic when delivered by mRNA and were mainly recognized by CD4 + T cells 176 . On the basis of these data, they generated a computational method to predict major histocompatibility complex (MHC) class II-restricted neoepitopes that can be used as vaccine immunogens. mRNA vaccines encoding such neoepitopes have controlled tumour growth in B16-F10 melanoma and CT26 colon cancer mouse models. In a recent clinical trial, Sahin and colleagues developed personalized neoepitope-based mRNA vaccines for 13 patients with metastatic melanoma, a cancer known for its high frequency of somatic mutations and thus neoepitopes. They immunized against ten neoepitopes per individual by injecting naked mRNA intranodally. CD4 + T cell responses were detected against the majority of the neoepitopes, and a low frequency of metastatic disease was observed after several months of follow-up 68 . Interestingly, similar results were also obtained in a study of analogous design that used synthetic peptides as immunogens rather than mRNA 177 . Together, these recent trials suggest the potential utility of the personalized vaccine methodology.

Box 3: The germinal centre and T follicular helper cells

The vast majority of potent antimicrobial vaccines elicit long-lived, protective antibody responses against the target pathogen. High-affinity antibodies are produced in specialized microanatomical sites within the B cell follicles of secondary lymphoid organs called germinal centres (GCs). B cell proliferation, somatic hypermutation and selection for high-affinity mutants occur in the GCs, and efficient T cell help is required for these processes 178 . Characterization of the relationship between GC B and T cells has been actively studied in recent years. The follicular homing receptor CXC-chemokine receptor 5 (CXCR5) was identified on GC B and T cells in the 1990s 179 , 180 , but the concept of a specific lineage of T follicular helper (T FH ) cells was not proposed until 2000 (Refs 181 , 182 ). The existence of the T FH lineage was confirmed in 2009 when the transcription factor specific for T FH cells, B cell lymphoma 6 protein (BCL-6), was identified 183 , 184 , 185 . T FH cells represent a specialized subset of CD4 + T cells that produce critical signals for B cell survival, proliferation and differentiation in addition to signals for isotype switching of antibodies and for the introduction of diversifying mutations into the immunoglobulin genes. The major cytokines produced by T FH cells are interleukin-4 (IL-4) and IL-21, which play a key role in driving the GC reaction. Other important markers and functional ligands expressed by T FH cells include CD40 ligand (CD40L), Src homology domain 2 (SH2) domain-containing protein 1A (SH2D1A), programmed cell death protein 1 (PD1) and inducible T cell co-stimulator (ICOS) 186 . The characterization of rare, broadly neutralizing antibodies to HIV-1 has revealed that unusually high rates of somatic hypermutation are a hallmark of protective antibody responses against HIV-1 (Ref. 187 ). As T FH cells play a key role in driving this process in GC reactions, the development of new adjuvants or vaccine platforms that can potently activate this cell type is urgently needed.

mRNA vaccines against infectious diseases

Development of prophylactic or therapeutic vaccines against infectious pathogens is the most efficient means to contain and prevent epidemics. However, conventional vaccine approaches have largely failed to produce effective vaccines against challenging viruses that cause chronic or repeated infections, such as HIV-1, herpes simplex virus and respiratory syncytial virus (RSV). Additionally, the slow pace of commercial vaccine development and approval is inadequate to respond to the rapid emergence of acute viral diseases, as illustrated by the 2014–2016 outbreaks of the Ebola and Zika viruses. Therefore, the development of more potent and versatile vaccine platforms is crucial.

Preclinical studies have created hope that mRNA vaccines will fulfil many aspects of an ideal clinical vaccine: they have shown a favourable safety profile in animals, are versatile and rapid to design for emerging infectious diseases, and are amenable to scalable good manufacturing practice (GMP) production (already under way by several companies). Unlike protein immunization, several formats of mRNA vaccines induce strong CD8 + T cell responses, likely owing to the efficient presentation of endogenously produced antigens on MHC class I molecules, in addition to potent CD4 + T cell responses 56 , 87 , 88 . Additionally, unlike DNA immunization, mRNA vaccines have shown the ability to generate potent neutralizing antibody responses in animals with only one or two low-dose immunizations 20 , 22 , 85 . As a result, mRNA vaccines have elicited protective immunity against a variety of infectious agents in animal models 19 , 20 , 22 , 56 , 89 , 90 and have therefore generated substantial optimism. However, recently published results from two clinical trials of mRNA vaccines for infectious diseases were somewhat modest, leading to more cautious expectations about the translation of preclinical success to the clinic 22 , 91 (discussed further below).

Two major types of RNA vaccine have been utilized against infectious pathogens: self-amplifying or replicon RNA vaccines and non-replicating mRNA vaccines. Non-replicating mRNA vaccines can be further distinguished by their delivery method: ex vivo loading of DCs or direct in vivo injection into a variety of anatomical sites. As discussed below, a rapidly increasing number of preclinical studies in these areas have been published recently, and several have entered human clinical trials ( Table 2 ).

Self-amplifying mRNA vaccines

Most currently used self-amplifying mRNA (SAM) vaccines are based on an alphavirus genome 92 , where the genes encoding the RNA replication machinery are intact but the genes encoding the structural proteins are replaced with the antigen of interest. The full-length RNA is ~9 kb long and can be easily produced by IVT from a DNA template. The SAM platform enables a large amount of antigen production from an extremely small dose of vaccine owing to intracellular replication of the antigen-encoding RNA. An early study reported that immunization with 10 μg of naked SAM vaccine encoding RSV fusion (F), influenza virus haemagglutinin (HA) or louping ill virus pre-membrane and envelope (prM-E) proteins resulted in antibody responses and partial protection from lethal viral challenges in mice 93 . The development of RNA complexing agents brought remarkable improvement to the efficacy of SAM vaccines. As little as 100 ng of an RNA replicon vaccine encoding RSV F, complexed to LNP, resulted in potent T and B cell immune responses in mice, and 1 μg elicited protective immune responses against RSV infection in a cotton rat intranasal challenge system 19 . SAM vaccines encoding influenza virus antigens in LNPs or an oil-in-water cationic nanoemulsion induced potent immune responses in ferrets and conferred protection from homologous and heterologous viral challenge in mice 94 , 95 , 96 . Further studies demonstrated the immunogenicity of this vaccine platform against diverse viruses in multiple species, including human cytomegalovirus (CMV), hepatitis C virus and rabies virus in mice, HIV-1 in rabbits, and HIV-1 and human CMV in rhesus macaques 50 , 87 , 97 . Replicon RNA encoding influenza antigens, complexed with chitosan-containing LNPs or polyethylenimine (PEI), has elicited T and B cell immune responses in mice after subcutaneous delivery 98 , 99 . Chahal and colleagues developed a delivery platform consisting of a chemically modified, ionizable dendrimer complexed into LNPs 89 . Using this platform, they demonstrated that intramuscular delivery of RNA replicons encoding influenza virus, Ebola virus or Toxoplasma gondii antigens protected mice against lethal infection 89 . The same group recently demonstrated that vaccination with an RNA replicon encoding Zika virus prM-E formulated in the same manner elicited antigen-specific antibody and CD8 + T cell responses in mice 88 . Another recent study reported immunogenicity and moderate protective efficacy of SAM vaccines against bacterial pathogens, namely Streptococcus (groups A and B) spp., further demonstrating the versatility of this platform 100 .

One of the advantages of SAM vaccines is that they create their own adjuvants in the form of dsRNA structures, replication intermediates and other motifs that may contribute to their high potency. However, the intrinsic nature of these PAMPs may make it difficult to modulate the inflammatory profile or reactogenicity of SAM vaccines. Additionally, size constraints of the insert are greater for SAM vaccines than for mRNAs that do not encode replicon genes, and the immunogenicity of the replication proteins may theoretically limit repeated use.

Dendritic cell mRNA vaccines

As described above, ex vivo DC loading is a heavily pursued method to generate cell-mediated immunity against cancer. Development of infectious disease vaccines using this approach has been mainly limited to a therapeutic vaccine for HIV-1: HIV-1-infected individuals on highly active antiretroviral therapy were treated with autologous DCs electroporated with mRNA encoding various HIV-1 antigens, and cellular immune responses were evaluated 101 , 102 , 103 , 104 , 105 , 106 . This intervention proved to be safe and elicited antigen-specific CD4 + and CD8 + T cell responses, but no clinical benefit was observed. Another study in humans evaluated a CMV pp65 mRNA-loaded DC vaccination in healthy human volunteers and allogeneic stem cell recipients and reported induction or expansion of CMV-specific cellular immune responses 107 .

Direct injection of non-replicating mRNA vaccines

Directly injectable, non-replicating mRNA vaccines are an appealing vaccine format owing to their simple and economical administration, particularly in resource-limited settings. Although an early report demonstrated that immunization with liposome-complexed mRNA encoding influenza virus nucleoproteins elicited CTL responses in mice 108 , the first demonstration of protective immune responses by mRNA vaccines against infectious pathogens was published only a few years ago 18 . This seminal work demonstrated that intradermally administered uncomplexed mRNA encoding various influenza virus antigens combined with a protamine-complexed RNA adjuvant was immunogenic in multiple animal models and protected mice from lethal viral challenge.

Immunization with the protamine-based RNActive platform encoding rabies virus glycoprotein has also induced protective immunity against a lethal intracerebral virus challenge in mice and potent neutralizing antibody responses in pigs 56 . In a recently published seminal work, Alberer and colleagues evaluated the safety and immunogenicity of this vaccine in 101 healthy human volunteers 91 . Subjects received 80–640 μg of mRNA vaccine three times by needle-syringe or needle-free devices, either intradermally or intramuscularly. Seven days after vaccination, nearly all participants reported mild to moderate injection site reactions, and 78% experienced a systemic reaction (for example, fever, headache and chills). There was one serious adverse event that was possibly related to the vaccine: a transient and moderate case of Bell palsy. Surprisingly, the needle-syringe injections did not generate detectable neutralizing antibodies in 98% of recipients. By contrast, needle-free delivery induced variable levels of neutralizing antibodies, the majority of which peaked above the expected protective threshold but then largely waned after 1 year in subjects who were followed up long term. Elucidating the basis of the disparate immunogenicity between the animals and humans who received this vaccine and between the two routes of delivery will be informative for future vaccine design using this platform.

Other infectious disease vaccines have successfully utilized lipid- or polymer-based delivery systems. Cationic 1,2-dioleoyloxy-3-trimethylammoniumpropane (DOTAP) and dioleoylphosphatidylethanolamine (DOPE) lipid-complexed mRNA encoding HIV-1 gag generated antigen-specific CD4 + and CD8 + T cell responses after subcutaneous delivery in mice 109 . Two other studies demonstrated that PEI-complexed mRNAs could be efficiently delivered to mice to induce HIV-1-specific immune responses: subcutaneously delivered mRNA encoding HIV-1 gag elicited CD4 + and CD8 + T cell responses, and intranasally administered mRNA encoding the HIV-1 envelope gp120 subunit crossed the nasal epithelium and generated antigen-specific immune responses in the nasal cavity 110 , 111 . Kranz and colleagues also performed intravenous immunizations in mice using lipid-complexed mRNA encoding influenza virus HA and showed evidence of T cell activation after a single dose 59 .

Nucleoside-modified mRNA vaccines represent a new and highly efficacious category of mRNA vaccines. Owing to the novelty of this immunization platform, our knowledge of efficacy is limited to the results of four recent publications that demonstrated the potency of such vaccines in small and large animals. The first published report demonstrated that a single intradermal injection of LNP-formulated mRNA encoding Zika virus prM-E, modified with 1-methylpseudouridine and FPLC purification, elicited protective immune responses in mice and rhesus macaques with the use of as little as 50 μg (0.02 mg kg −1 ) of vaccine in macaques 20 . A subsequent study by a different group tested a similarly designed vaccine against Zika virus in mice and found that a single intramuscular immunization elicited moderate immune responses, and a booster vaccination resulted in potent and protective immune responses 85 . This vaccine also incorporated the modified nucleoside 1-methylpseudouridine, but FPLC purification or other methods of removing dsRNA contaminants were not reported. Notably, this report showed that antibody-dependent enhancement of secondary infection with a heterologous flavivirus, a major concern for dengue and Zika virus vaccines, could be diminished by removing a cross-reactive epitope in the E protein. A recent follow-up study evaluated the same vaccine in a model of maternal vaccination and fetal infection 112 . Two immunizations reduced Zika virus infection in fetal mice by several orders of magnitude and completely rescued a defect in fetal viability.

Another recent report evaluated the immunogenicity of LNP-complexed, nucleoside-modified, non-FPLC-purified mRNA vaccines against influenza HA 10 neuraminidase 8 (H10N8) and H7N9 influenza viruses in mice, ferrets, non-human primates and, for the first time, humans 22 . A single intradermal or intramuscular immunization with low doses (0.4–10 μg) of LNP-complexed mRNA encoding influenza virus HA elicited protective immune responses against homologous influenza virus challenge in mice. Similar results were obtained in ferrets and cynomolgus monkeys after immunization with one or two doses of 50–400 μg of a vaccine containing LNP-complexed mRNA encoding HA, corroborating that the potency of mRNA–LNP vaccines translates to larger animals, including non-human primates.

On the basis of encouraging preclinical data, two phase I clinical trials have recently been initiated to evaluate the immunogenicity and safety of nucleoside-modified mRNA–LNP vaccines in humans for the first time. The mRNA vaccine encoding H10N8 HA is currently undergoing clinical testing (NCT03076385), and interim findings for 23 vaccinated individuals have been reported 22 . Participants received a small amount (100 μg) of vaccine intramuscularly, and immunogenicity was measured 43 days after vaccination. The vaccine proved to be immunogenic in all subjects, as measured by haemagglutination inhibition and microneutralization antibody assays. Promisingly, antibody titres were above the expected protective threshold, but they were moderately lower than in the animal models. Similarly to the study by Alberer et al . 91 , most vaccinated subjects reported mild to moderate reactogenicity (injection site pain, myalgia, headache, fatigue and chills), and three subjects reported severe injection site reactions or a systemic common cold-like response. This level of reactogenicity appears to be similar to that of more traditional vaccine formats 113 , 114 . Finally, the Zika virus vaccine described by Richner et al . 85 , 112 is also entering clinical evaluation in a combined phase I/II trial (NCT03014089). Future studies that apply nucleoside-modified mRNA–LNP vaccines against a greater diversity of antigens will reveal the extent to which this strategy is broadly applicable to infectious disease vaccines.

mRNA cancer vaccines

mRNA-based cancer vaccines have been recently and extensively reviewed 115 , 116 , 117 , 118 , 119 . Below, the most recent advances and directions are highlighted. Cancer vaccines and other immunotherapies represent promising alternative strategies to treat malignancies. Cancer vaccines can be designed to target tumour-associated antigens that are preferentially expressed in cancerous cells, for example, growth-associated factors, or antigens that are unique to malignant cells owing to somatic mutation 120 . These neoantigens, or the neoepitopes within them, have been deployed as mRNA vaccine targets in humans 121 ( Box 2 ). Most cancer vaccines are therapeutic, rather than prophylactic, and seek to stimulate cell-mediated responses, such as those from CTLs, that are capable of clearing or reducing tumour burden 122 . The first proof-of-concept studies that not only proposed the idea of RNA cancer vaccines but also provided evidence of the feasibility of this approach were published more than two decades ago 123 , 124 . Since then, numerous preclinical and clinical studies have demonstrated the viability of mRNA vaccines to combat cancer ( Table 3 ).

DC mRNA cancer vaccines

As DCs are central players in initiating antigen-specific immune responses, it seemed logical to utilize them for cancer immunotherapy. The first demonstration that DCs electroporated with mRNA could elicit potent immune responses against tumour antigens was reported by Boczkowski and colleagues in 1996 (Ref. 124 ). In this study, DCs pulsed with ovalbumin (OVA)-encoding mRNA or tumour-derived RNAs elicited a tumour-reducing immune response in OVA-expressing and other melanoma models in mice. A variety of immune regulatory proteins have been identified in the form of mRNA-encoded adjuvants that can increase the potency of DC cancer vaccines. Several studies demonstrated that electroporation of DCs with mRNAs encoding co-stimulatory molecules such as CD83, tumour necrosis factor receptor superfamily member 4 (TNFRSF4; also known as OX40) and 4-1BB ligand (4-1BBL) resulted in a substantial increase in the immune stimulatory activity of DCs 125 , 126 , 127 , 128 . DC functions can also be modulated through the use of mRNA-encoded pro-inflammatory cytokines, such as IL-12, or trafficking-associated molecules 129 , 130 , 131 . As introduced above, TriMix is a cocktail of mRNA-encoded adjuvants (CD70, CD40L and constitutively active TLR4) that can be electroporated in combination with antigen-encoding mRNA or mRNAs 132 . This formulation proved efficacious in multiple preclinical studies by increasing DC activation and shifting the CD4 + T cell phenotype from T regulatory cells to T helper 1 (T H 1)-like cells 132 , 133 , 134 , 135 , 136 . Notably, the immunization of patients with stage III or stage IV melanoma using DCs loaded with mRNA encoding melanoma-associated antigens and TriMix adjuvant resulted in tumour regression in 27% of treated individuals 137 . Multiple clinical trials have now been conducted using DC vaccines targeting various cancer types, such as metastatic prostate cancer, metastatic lung cancer, renal cell carcinoma, brain cancers, melanoma, acute myeloid leukaemia, pancreatic cancer and others 138 , 139 (reviewed in Refs 51 , 58 ).

A new line of research combines mRNA electroporation of DCs with traditional chemotherapy agents or immune checkpoint inhibitors. In one trial, patients with stage III or IV melanoma were treated with ipilimumab, a monoclonal antibody against CTL antigen 4 (CTLA4), and DCs loaded with mRNA encoding melanoma-associated antigens plus TriMix. This intervention resulted in durable tumour reduction in a proportion of individuals with recurrent or refractory melanoma 140 .

Direct injection of mRNA cancer vaccines

The route of administration and delivery format of mRNA vaccines can greatly influence outcomes. A variety of mRNA cancer vaccine formats have been developed using common delivery routes (intradermal, intramuscular, subcutaneous or intranasal) and some unconventional routes of vaccination (intranodal, intravenous, intrasplenic or intratumoural).

Intranodal administration of naked mRNA is an unconventional but efficient means of vaccine delivery. Direct mRNA injection into secondary lymphoid tissue offers the advantage of targeted antigen delivery to antigen-presenting cells at the site of T cell activation, obviating the need for DC migration. Several studies have demonstrated that intranodally injected naked mRNA can be selectively taken up by DCs and can elicit potent prophylactic or therapeutic antitumour T cell responses 62 , 66 ; an early study also demonstrated similar findings with intrasplenic delivery 141 . Coadministration of the DC-activating protein FMS-related tyrosine kinase 3 ligand (FLT3L) was shown in some cases to further improve immune responses to intranodal mRNA vaccination 142 , 143 . Incorporation of the TriMix adjuvant into intranodal injections of mice with mRNAs encoding tumour-associated antigens resulted in potent antigen-specific CTL responses and tumour control in multiple tumour models 133 . A more recent study demonstrated that intranodal injection of mRNA encoding the E7 protein of human papillomavirus (HPV) 16 with TriMix increased the number of tumour-infiltrating CD8 + T cells and inhibited the growth of an E7-expressing tumour model in mice 67 .

The success of preclinical studies has led to the initiation of clinical trials using intranodally injected naked mRNA encoding tumour-associated antigens into patients with advanced melanoma (NCT01684241) and patients with hepatocellular carcinoma (EudraCT: 2012-005572-34). In one published trial, patients with metastatic melanoma were treated with intranodally administered DCs electroporated with mRNA encoding the melanoma-associated antigens tyrosinase or gp100 and TriMix, which induced limited antitumour responses 144 .

Intranasal vaccine administration is a needle-free, noninvasive manner of delivery that enables rapid antigen uptake by DCs. Intranasally delivered mRNA complexed with Stemfect (Stemgent) LNPs resulted in delayed tumour onset and increased survival in prophylactic and therapeutic mouse tumour models using the OVA-expressing E.G7-OVA T lymphoblastic cell line 145 .

Intratumoural mRNA vaccination is a useful approach that offers the advantage of rapid and specific activation of tumour-resident T cells. Often, these vaccines do not introduce mRNAs encoding tumour-associated antigens but simply aim to activate tumour-specific immunity in situ using immune stimulatory molecules. An early study demonstrated that naked mRNA or protamine-stabilized mRNA encoding a non-tumour related gene ( GLB1 ) impaired tumour growth and provided protection in a glioblastoma mouse model, taking advantage of the intrinsic immunogenic properties of mRNA 146 . A more recent study showed that intratumoural delivery of mRNA encoding an engineered cytokine based on interferon-β (IFNβ) fused to a transforming growth factor-β (TGFβ) antagonist increased the cytolytic capacity of CD8 + T cells and modestly delayed tumour growth in OVA-expressing lymphoma or lung carcinoma mouse models 147 . It has also been shown that intratumoural administration of TriMix mRNA that does not encode tumour-associated antigens results in activation of CD8α + DCs and tumour-specific T cells, leading to delayed tumour growth in various mouse models 148 .

Systemic administration of mRNA vaccines is not common owing to concerns about aggregation with serum proteins and rapid extracellular mRNA degradation; thus, formulating mRNAs into carrier molecules is essential. As discussed above, numerous delivery formulations have been developed to facilitate mRNA uptake, increase protein translation and protect mRNA from RNases 10 , 11 , 79 , 80 . Another important issue is the biodistribution of mRNA vaccines after systemic delivery. Certain cationic LNP-based complexing agents delivered intravenously traffic mainly to the liver 21 , which may not be ideal for DC activation. An effective strategy for DC targeting of mRNA vaccines after systemic delivery has recently been described 59 . An mRNA–lipoplex (mRNA–liposome complex) delivery platform was generated using cationic lipids and neutral helper lipids formulated with mRNA, and it was discovered that the lipid-to-mRNA ratio, and thus the net charge of the particles, has a profound impact on the biodistribution of the vaccine. While a positively charged lipid particle primarily targeted the lung, a negatively charged particle targeted DCs in secondary lymphoid tissues and bone marrow. The negatively charged particle induced potent immune responses against tumour-specific antigens that were associated with impressive tumour reduction in various mouse models 59 . As no toxic effects were observed in mice or non-human primates, clinical trials using this approach to treat patients with advanced melanoma or triple-negative breast cancer have been initiated (NCT02410733 and NCT02316457).

A variety of antigen-presenting cells reside in the skin 149 , making it an ideal site for immunogen delivery during vaccination ( Fig. 3 ). Thus, the intradermal route of delivery has been widely used for mRNA cancer vaccines. An early seminal study demonstrated that intradermal administration of total tumour RNA delayed tumour growth in a fibrosarcoma mouse model 65 . Intradermal injection of mRNA encoding tumour antigens in the protamine-based RNActive platform proved efficacious in various mouse models of cancer 36 and in multiple prophylactic and therapeutic clinical settings ( Table 3 ). One such study demonstrated that mRNAs encoding survivin and various melanoma tumour antigens resulted in increased numbers of antigen-specific T cells in a subset of patients with melanoma 150 . In humans with castration-resistant prostate cancer, an RNActive vaccine expressing multiple prostate cancer-associated proteins elicited antigen-specific T cell responses in the majority of recipients 151 . Lipid-based carriers have also contributed to the efficacy of intradermally delivered mRNA cancer vaccines. The delivery of OVA-encoding mRNA in DOTAP and/or DOPE liposomes resulted in antigen-specific CTL activity and inhibited growth of OVA-expressing tumours in mice 152 . In the same study, coadministration of mRNA encoding granulocyte–macrophage colony-stimulating factor (GM-CSF) improved OVA-specific cytolytic responses. Another report showed that subcutaneous delivery of LNP-formulated mRNA encoding two melanoma-associated antigens delayed tumour growth in mice, and co-delivery of lipopolysaccharide (LPS) in LNPs increased both CTL and antitumour activity 153 . In general, mRNA cancer vaccines have proved immunogenic in humans, but further refinement of vaccination methods, as informed by basic immunological research, will likely be necessary to achieve greater clinical benefits.

For an injected mRNA vaccine, major considerations for effectiveness include the following: the level of antigen expression in professional antigen-presenting cells (APCs), which is influenced by the efficiency of the carrier, by the presence of pathogen-associated molecular patterns (PAMPs) in the form of double-stranded RNA (dsRNA) or unmodified nucleosides and by the level of optimization of the RNA sequence (codon usage, G:C content, 5′ and 3′ untranslated regions (UTRs) and so on); dendritic cell (DC) maturation and migration to secondary lymphoid tissue, which is increased by PAMPs; and the ability of the vaccine to activate robust T follicular helper (T FH ) cell and germinal centre (GC) B cell responses — an area that remains poorly understood. An intradermal injection is shown as an example. EC, extracellular.

The combination of mRNA vaccination with adjunctive therapies, such as traditional chemotherapy, radiotherapy and immune checkpoint inhibitors, has increased the beneficial outcome of vaccination in some preclinical studies 154 , 155 . For example, cisplatin treatment significantly increased the therapeutic effect of immunizing with mRNA encoding the HPV16 E7 oncoprotein and TriMix, leading to the complete rejection of female genital tract tumours in a mouse model 67 . Notably, it has also been suggested that treatment with antibodies against programmed cell death protein 1 (PD1) increased the efficacy of a neoepitope mRNA-based vaccine against metastatic melanoma in humans, but more data are required to explore this hypothesis 68 .

Therapeutic considerations and challenges

Good manufacturing practice production.

mRNA is produced by in vitro reactions with recombinant enzymes, ribonucleotide triphosphates (NTPs) and a DNA template; thus, it is rapid and relatively simple to produce in comparison with traditional protein subunit and live or inactivated virus vaccine production platforms. Its reaction yield and simplicity make rapid mRNA production possible in a small GMP facility footprint. The manufacturing process is sequence-independent and is primarily dictated by the length of the RNA, the nucleotide and capping chemistry and the purification of the product; however, it is possible that certain sequence properties such as extreme length may present difficulties (D.W., unpublished observations). According to current experience, the process can be standardized to produce nearly any encoded protein immunogen, making it particularly suitable for rapid response to emerging infectious diseases.

All enzymes and reaction components required for the GMP production of mRNA can be obtained from commercial suppliers as synthesized chemicals or bacterially expressed, animal component-free reagents, thereby avoiding safety concerns surrounding the adventitious agents that plague cell-culture-based vaccine manufacture. All the components, such as plasmid DNA, phage polymerases, capping enzymes and NTPs, are readily available as GMP-grade traceable components; however, some of these are currently available at only limited scale or high cost. As mRNA therapeutics move towards commercialization and the scale of production increases, more economical options may become accessible for GMP source materials.

GMP production of mRNA begins with DNA template production followed by enzymatic IVT and follows the same multistep protocol that is used for research scale synthesis, with added controls to ensure the safety and potency of the product 16 . Depending on the specific mRNA construct and chemistry, the protocol may be modified slightly from what is described here to accommodate modified nucleosides, capping strategies or template removal. To initiate the production process, template plasmid DNA produced in Escherichia coli is linearized using a restriction enzyme to allow synthesis of runoff transcripts with a poly(A) tract at the 3′ end. Next, the mRNA is synthesized from NTPs by a DNA-dependent RNA polymerase from bacteriophage (such as T7, SP6, or T3). The template DNA is then degraded by incubation with DNase. Finally, the mRNA is enzymatically or chemically capped to enable efficient translation in vivo . mRNA synthesis is highly productive, yielding in excess of 2 g l −1 of full-length mRNA in multi-gram scale reactions under optimized conditions.

Once the mRNA is synthesized, it is processed though several purification steps to remove reaction components, including enzymes, free nucleotides, residual DNA and truncated RNA fragments. While LiCl precipitation is routinely used for laboratory-scale preparation, purification at the clinical scale utilizes derivatized microbeads in batch or column formats, which are easier to utilize at large scale 156 , 157 . For some mRNA platforms, removal of dsRNA and other contaminants is critical for the potency of the final product, as it is a potent inducer of interferon-dependent translation inhibition. This has been accomplished by reverse-phase FPLC at the laboratory scale 158 , and scalable aqueous purification approaches are being investigated. After mRNA is purified, it is exchanged into a final storage buffer and sterile-filtered for subsequent filling into vials for clinical use. RNA is susceptible to degradation by both enzymatic and chemical pathways 157 . Formulation buffers are tested to ensure that they are free of contaminating RNases and may contain buffer components, such as antioxidants and chelators, which minimize the effects of reactive oxygen species and divalent metal ions that lead to mRNA instability 159 .

Pharmaceutical formulation of mRNAs is an active area of development. Although most products for early phase studies are stored frozen (−70 °C), efforts to develop formulations that are stable at higher temperatures more suitable for vaccine distribution are continuing. Published reports suggest that stable refrigerated or room temperature formulations can be made. The RNActive platform was reported to be active after lyophilization and storage at 5–25 °C for 3 years and at 40 °C for 6 months 91 . Another report demonstrated that freeze-dried naked mRNA is stable for at least 10 months under refrigerated conditions 160 . The stability of mRNA products might also be improved by packaging within nanoparticles or by co-formulation with RNase inhibitors 161 . For lipid-encapsulated mRNA, at least 6 months of stability has been observed (Arbutus Biopharma, personal communication), but longer-term storage of such mRNA–lipid complexes in an unfrozen form has not yet been reported.

Regulatory aspects

There is no specific guidance from the FDA or European Medicines Agency (EMA) for mRNA vaccine products. However, the increasing number of clinical trials conducted under EMA and FDA oversight indicate that regulators have accepted the approaches proposed by various organizations to demonstrate that products are safe and acceptable for testing in humans. Because mRNA falls into the broad vaccine category of genetic immunogens, many of the guiding principles that have been defined for DNA vaccines 162 and gene therapy vectors 163 , 164 can likely be applied to mRNA with some adaptations to reflect the unique features of mRNA. A detailed review of EMA regulations for RNA vaccines by Hinz and colleagues highlights the different regulatory paths stipulated for prophylactic infectious disease versus therapeutic applications 165 . Regardless of the specific classification within existing guidelines, some themes can be observed in what is stated in these guidance documents and in what has been reported for recently published clinical studies. In particular, the recent report of an mRNA vaccine against influenza virus highlights preclinical and clinical data demonstrating biodistribution and persistence in mice, disease protection in a relevant animal model (ferrets), and immunogenicity, local reactogenicity and toxicity in humans 22 . As mRNA products become more prominent in the vaccine field, it is likely that specific guidance will be developed that will delineate requirements to produce and evaluate new mRNA vaccines.

The requirement for safety in modern prophylactic vaccines is extremely stringent because the vaccines are administered to healthy individuals. Because the manufacturing process for mRNA does not require toxic chemicals or cell cultures that could be contaminated with adventitious viruses, mRNA production avoids the common risks associated with other vaccine platforms, including live virus, viral vectors, inactivated virus and subunit protein vaccines. Furthermore, the short manufacturing time for mRNA presents few opportunities to introduce contaminating microorganisms. In vaccinated people, the theoretical risks of infection or integration of the vector into host cell DNA are not a concern for mRNA. For the above reasons, mRNA vaccines have been considered a relatively safe vaccine format.

Several different mRNA vaccines have now been tested from phase I to IIb clinical studies and have been shown to be safe and reasonably well tolerated ( Tables 2 , 3 ). However, recent human trials have demonstrated moderate and in rare cases severe injection site or systemic reactions for different mRNA platforms 22 , 91 . Potential safety concerns that are likely to be evaluated in future preclinical and clinical studies include local and systemic inflammation, the biodistribution and persistence of expressed immunogen, stimulation of auto-reactive antibodies and potential toxic effects of any non-native nucleotides and delivery system components. A possible concern could be that some mRNA-based vaccine platforms 54 , 166 induce potent type I interferon responses, which have been associated not only with inflammation but also potentially with autoimmunity 167 , 168 . Thus, identification of individuals at an increased risk of autoimmune reactions before mRNA vaccination may allow reasonable precautions to be taken. Another potential safety issue could derive from the presence of extracellular RNA during mRNA vaccination. Extracellular naked RNA has been shown to increase the permeability of tightly packed endothelial cells and may thus contribute to oedema 169 . Another study showed that extracellular RNA promoted blood coagulation and pathological thrombus formation 170 . Safety will therefore need continued evaluation as different mRNA modalities and delivery systems are utilized for the first time in humans and are tested in larger patient populations.

Conclusions and future directions

Currently, mRNA vaccines are experiencing a burst in basic and clinical research. The past 2 years alone have witnessed the publication of dozens of preclinical and clinical reports showing the efficacy of these platforms. Whereas the majority of early work in mRNA vaccines focused on cancer applications, a number of recent reports have demonstrated the potency and versatility of mRNA to protect against a wide variety of infectious pathogens, including influenza virus, Ebola virus, Zika virus, Streptococcus spp. and T. gondii ( Tables 1 , 2 ).

While preclinical studies have generated great optimism about the prospects and advantages of mRNA-based vaccines, two recent clinical reports have led to more tempered expectations 22 , 91 . In both trials, immunogenicity was more modest in humans than was expected based on animal models, a phenomenon also observed with DNA-based vaccines 171 , and the side effects were not trivial. We caution that these trials represent only two variations of mRNA vaccine platforms, and there may be substantial differences when the expression and immunostimulatory profiles of the vaccine are changed. Further research is needed to determine how different animal species respond to mRNA vaccine components and inflammatory signals and which pathways of immune signalling are most effective in humans.

Recent advances in understanding and reducing the innate immune sensing of mRNA have aided efforts not only in active vaccination but also in several applications of passive immunization or passive immunotherapy for infectious diseases and cancer ( Box 4 ). Direct comparisons between mRNA expression platforms should clarify which systems are most appropriate for both passive and active immunization. Given the large number of promising mRNA platforms, further head-to-head comparisons would be of utmost value to the vaccine field because this would allow investigators to focus resources on those best suited for each application.

The fast pace of progress in mRNA vaccines would not have been possible without major recent advances in the areas of innate immune sensing of RNA and in vivo delivery methods. Extensive basic research into RNA and lipid and polymer biochemistry has made it possible to translate mRNA vaccines into clinical trials and has led to an astonishing level of investment in mRNA vaccine companies ( Table 4 ). Moderna Therapeutics, founded in 2010, has raised almost US$2 billion in capital with a plan to commercialize mRNA-based vaccines and therapies 172 , 173 . The US Biomedical Advanced Research and Development Authority (BARDA) has committed support for Moderna's clinical evaluation of a promising nucleoside-modified mRNA vaccine for Zika virus (NCT03014089). In Germany, CureVac AG has an expanding portfolio of therapeutic targets 174 , including both cancer and infectious diseases, and BioNTech is developing an innovative approach to personalized cancer medicine using mRNA vaccines 121 ( Box 2 ). The translation of basic research into clinical testing is also made more expedient by the commercialization of custom GMP products by companies such as New England Biolabs and Aldevron 175 . Finally, the recent launch of the Coalition for Epidemic Preparedness Innovations (CEPI) provides great optimism for future responses to emerging viral epidemics. This multinational public and private partnership aims to raise $1 billion to develop platform-based vaccines, such as mRNA, to rapidly contain emerging outbreaks before they spread out of control.

The future of mRNA vaccines is therefore extremely bright, and the clinical data and resources provided by these companies and other institutions are likely to substantially build on and invigorate basic research into mRNA-based therapeutics.

Box 4: mRNA-based passive immunotherapy

Recombinant monoclonal antibodies are rapidly transforming the pharmaceutical market and have become one of the most successful therapeutic classes to treat autoimmune disorders, infectious diseases, osteoporosis, hypercholesterolemia and cancer 188 , 189 , 190 , 191 , 192 . However, the high cost of protein production and the need for frequent systemic administration pose a major limitation to widespread accessibility. Antibody-gene transfer technologies could potentially overcome these difficulties, as they administer nucleotide sequences encoding monoclonal antibodies to patients, enabling in vivo production of properly folded and modified protein therapeutics 193 . Multiple gene therapy vectors have been investigated (for example, viral vectors and plasmid DNA) that bear limitations such as pre-existing host immunity, acquired anti-vector immunity, high innate immunogenicity, difficulties with in vivo regulation of antibody production and toxic effects 193 , 194 . mRNA therapeutics combine safety with exquisite dose control and the potential for multiple administrations with no pre-existing or anti-vector immunity. Two early reports demonstrated that dendritic cells (DCs) electroporated with mRNAs encoding antibodies against immuno-inhibitory proteins secreted functional antibodies and improved immune responses in mice 195 , 196 . Three recent publications have described the use of injectable mRNA for in vivo production of therapeutic antibodies: Pardi and colleagues demonstrated that a single intravenous injection into mice with lipid nanoparticle (LNP)-encapsulated nucleoside-modified mRNAs encoding the heavy and light chains of the anti-HIV-1 neutralizing antibody VRC01 rapidly produced high levels of functional antibody in the serum and protected humanized mice from HIV-1 infection 197 ; Stadler and co-workers demonstrated that intravenous administration of low doses of TransIT (Mirus Bio LLC)-complexed, nucleoside-modified mRNAs encoding various anticancer bispecific antibodies resulted in the elimination of large tumours in mouse models 198 ; and Thran and colleagues 199 utilized an unmodified mRNA–LNP delivery system 12 to express three monoclonal antibodies at levels that protected from lethal challenges with rabies virus, botulinum toxin and a B cell lymphoma cell line. No toxic effects were observed in any of these studies. These observations suggest that mRNA offers a safe, simple and efficient alternative to therapeutic monoclonal antibody protein delivery, with potential application to any therapeutic protein.

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World Health Organization. Immunization coverage. World Health Organization http://www.who.int/mediacentre/factsheets/fs378/en (2017).

Younger, D. S., Younger, A. P. & Guttmacher, S. Childhood vaccination: implications for global and domestic public health. Neurol. Clin. 34 , 1035–1047 (2016).

Article   PubMed   Google Scholar  

Plotkin, S. A. Vaccines: the fourth century. Clin. Vaccine Immunol. 16 , 1709–1719 (2009).

Article   CAS   PubMed Central   PubMed   Google Scholar  

Rodrigues, C. M. C., Pinto, M. V., Sadarangani, M. & Plotkin, S. A. Whither vaccines? J. Infect. 74 (Suppl. 1), S2–S9 (2017).

Article   PubMed   PubMed Central   Google Scholar  

Wolff, J. A. et al. Direct gene transfer into mouse muscle in vivo . Science 247 , 1465–1468 (1990). This study demonstrates protein production from RNA administered in vivo .

Article   CAS   PubMed   Google Scholar  

Jirikowski, G. F., Sanna, P. P., Maciejewski-Lenoir, D. & Bloom, F. E. Reversal of diabetes insipidus in Brattleboro rats: intrahypothalamic injection of vasopressin mRNA. Science 255 , 996–998 (1992).

Suschak, J. J., Williams, J. A. & Schmaljohn, C. S. Advancements in DNA vaccine vectors, non-mechanical delivery methods, and molecular adjuvants to increase immunogenicity. Hum. Vaccin. Immunother. 13 , 2837–2848 (2017).

Article   PubMed Central   PubMed   Google Scholar  

Tandrup Schmidt, S., Foged, C., Korsholm, K. S., Rades, T. & Christensen, D. Liposome-based adjuvants for subunit vaccines: formulation strategies for subunit antigens and immunostimulators. Pharmaceutics 8 , E7 (2016).

Article   PubMed   CAS   Google Scholar  

Kariko, K. et al. Incorporation of pseudouridine into mRNA yields superior nonimmunogenic vector with increased translational capacity and biological stability. Mol. Ther. 16 , 1833–1840 (2008).

Kauffman, K. J., Webber, M. J. & Anderson, D. G. Materials for non-viral intracellular delivery of messenger RNA therapeutics. J. Control. Release 240 , 227–234 (2016).

Guan, S. & Rosenecker, J. Nanotechnologies in delivery of mRNA therapeutics using nonviral vector-based delivery systems. Gene Ther. 24 , 133–143 (2017).

Thess, A. et al. Sequence-engineered mRNA without chemical nucleoside modifications enables an effective protein therapy in large animals. Mol. Ther. 23 , 1456–1464 (2015).

Kariko, K., Muramatsu, H., Ludwig, J. & Weissman, D. Generating the optimal mRNA for therapy: HPLC purification eliminates immune activation and improves translation of nucleoside-modified, protein-encoding mRNA. Nucleic Acids Res. 39 , e142 (2011). This study demonstrates the importance of purification of IVT mRNA in achieving potent protein translation and in suppressing inflammatory responses.

Weissman, D. mRNA transcript therapy. Expert Rev. Vaccines 14 , 265–281 (2015).

Sahin, U., Kariko, K. & Tureci, O. mRNA-based therapeutics — developing a new class of drugs. Nat. Rev. Drug Discov. 13 , 759–780 (2014). This is a useful Review covering vaccine and non-vaccine forms of mRNA therapeutics.

Pardi, N., Muramatsu, H., Weissman, D. & Kariko, K. In vitro transcription of long RNA containing modified nucleosides. Methods Mol. Biol. 969 , 29–42 (2013).

Tsui, N. B., Ng, E. K. & Lo, Y. M. Stability of endogenous and added RNA in blood specimens, serum, and plasma. Clin. Chem. 48 , 1647–1653 (2002).

Petsch, B. et al. Protective efficacy of in vitro synthesized, specific mRNA vaccines against influenza A virus infection. Nat. Biotechnol. 30 , 1210–1216 (2012). This study demonstrates that directly injected, non-replicating mRNA can induce protective immune responses against an infectious pathogen.

Geall, A. J. et al. Nonviral delivery of self-amplifying RNA vaccines. Proc. Natl Acad. Sci. USA 109 , 14604–14609 (2012). This important study demonstrates that the duration of in vivo protein production from RNA replicons can be greatly improved by packaging them into lipid nanoparticles.

Article   CAS   PubMed   PubMed Central   Google Scholar  

Pardi, N. et al. Zika virus protection by a single low-dose nucleoside-modified mRNA vaccination. Nature 543 , 248–251 (2017).

Pardi, N. et al. Expression kinetics of nucleoside-modified mRNA delivered in lipid nanoparticles to mice by various routes. J. Control. Release 217 , 345–351 (2015).

Bahl, K. et al. Preclinical and clinical demonstration of immunogenicity by mRNA vaccines against H10N8 and H7N9 influenza viruses. Mol. Ther. 25 , 1316–1327 (2017). This is a report of a clinical vaccine trial using directly injected, non-replicating, nucleoside-modified mRNA against an infectious pathogen.

Ross, J. & Sullivan, T. D. Half-lives of beta and gamma globin messenger RNAs and of protein synthetic capacity in cultured human reticulocytes. Blood 66 , 1149–1154 (1985).

Holtkamp, S. et al. Modification of antigen-encoding RNA increases stability, translational efficacy, and T-cell stimulatory capacity of dendritic cells. Blood 108 , 4009–4017 (2006).

Gallie, D. R. The cap and poly(A) tail function synergistically to regulate mRNA translational efficiency. Genes Dev. 5 , 2108–2116 (1991).

Martin, S. A., Paoletti, E. & Moss, B. Purification of mRNA guanylyltransferase and mRNA (guanine-7-) methyltransferase from vaccinia virions. J. Biol. Chem. 250 , 9322–9329 (1975).

Stepinski, J., Waddell, C., Stolarski, R., Darzynkiewicz, E. & Rhoads, R. E. Synthesis and properties of mRNAs containing the novel “anti-reverse” cap analogs 7-methyl(3′-O-methyl)GpppG and 7-methyl (3′-deoxy)GpppG. RNA 7 , 1486–1495 (2001).

CAS   PubMed Central   PubMed   Google Scholar  

Malone, R. W., Felgner, P. L. & Verma, I. M. Cationic liposome-mediated RNA transfection. Proc. Natl Acad. Sci. USA 86 , 6077–6081 (1989).

Gustafsson, C., Govindarajan, S. & Minshull, J. Codon bias and heterologous protein expression. Trends Biotechnol. 22 , 346–353 (2004).

Mauro, V. P. & Chappell, S. A. A critical analysis of codon optimization in human therapeutics. Trends Mol. Med. 20 , 604–613 (2014).

Kudla, G., Lipinski, L., Caffin, F., Helwak, A. & Zylicz, M. High guanine and cytosine content increases mRNA levels in mammalian cells. PLoS Biol. 4 , e180 (2006).

Article   PubMed Central   PubMed   CAS   Google Scholar  

Kudla, G., Murray, A. W., Tollervey, D. & Plotkin, J. B. Coding-sequence determinants of gene expression in Escherichia coli . Science 324 , 255–258 (2009).

Buhr, F. et al. Synonymous codons direct cotranslational folding toward different protein conformations. Mol. Cell 61 , 341–351 (2016).

Yu, C. H. et al. Codon usage influences the local rate of translation elongation to regulate co-translational protein folding. Mol. Cell 59 , 744–754 (2015).

Chen, N. et al. RNA sensors of the innate immune system and their detection of pathogens. IUBMB Life 69 , 297–304 (2017).

Fotin-Mleczek, M. et al. Messenger RNA-based vaccines with dual activity induce balanced TLR-7 dependent adaptive immune responses and provide antitumor activity. J. Immunother. 34 , 1–15 (2011).

Rettig, L. et al. Particle size and activation threshold: a new dimension of danger signaling. Blood 115 , 4533–4541 (2010).

de Haro, C., Mendez, R. & Santoyo, J. The eIF-2α kinases and the control of protein synthesis. FASEB J. 10 , 1378–1387 (1996).

Liang, S. L., Quirk, D. & Zhou, A. RNase L: its biological roles and regulation. IUBMB Life 58 , 508–514 (2006).

Zhang, Z. et al. Structural analysis reveals that Toll-like receptor 7 is a dual receptor for guanosine and single-stranded RNA. Immunity 45 , 737–748 (2016).

Tanji, H. et al. Toll-like receptor 8 senses degradation products of single-stranded RNA. Nat. Struct. Mol. Biol. 22 , 109–115 (2015).

Isaacs, A., Cox, R. A. & Rotem, Z. Foreign nucleic acids as the stimulus to make interferon. Lancet 2 , 113–116 (1963).

Schwartz, S. et al. Transcriptome-wide mapping reveals widespread dynamic-regulated pseudouridylation of ncRNA and mRNA. Cell 159 , 148–162 (2014).

Carlile, T. M. et al. Pseudouridine profiling reveals regulated mRNA pseudouridylation in yeast and human cells. Nature 515 , 143–146 (2014).

Andries, O. et al. N 1 -methylpseudouridine-incorporated mRNA outperforms pseudouridine-incorporated mRNA by providing enhanced protein expression and reduced immunogenicity in mammalian cell lines and mice. J. Control. Release 217 , 337–344 (2015).

Anderson, B. R. et al. Incorporation of pseudouridine into mRNA enhances translation by diminishing PKR activation. Nucleic Acids Res. 38 , 5884–5892 (2010).

Anderson, B. R. et al. Nucleoside modifications in RNA limit activation of 2′-5′-oligoadenylate synthetase and increase resistance to cleavage by RNase L. Nucleic Acids Res. 39 , 9329–9338 (2011).

Kariko, K., Buckstein, M., Ni, H. & Weissman, D. Suppression of RNA recognition by Toll-like receptors: the impact of nucleoside modification and the evolutionary origin of RNA. Immunity 23 , 165–175 (2005). This report demonstrates that nucleoside modification of mRNA decreases inflammatory responses.

Kauffman, K. J. et al. Efficacy and immunogenicity of unmodified and pseudouridine-modified mRNA delivered systemically with lipid nanoparticles in vivo . Biomaterials 109 , 78–87 (2016).

Brito, L. A. et al. A cationic nanoemulsion for the delivery of next-generation RNA vaccines. Mol. Ther. 22 , 2118–2129 (2014).

Van Lint, S. et al. The ReNAissanCe of mRNA-based cancer therapy. Expert Rev. Vaccines 14 , 235–251 (2015).

Kallen, K. J. et al. A novel, disruptive vaccination technology: self-adjuvanted RNActive ® vaccines. Hum. Vaccin Immunother. 9 , 2263–2276 (2013).

Rauch, S., Lutz, J., Kowalczyk, A., Schlake, T. & Heidenreich, R. RNActive ® technology: generation and testing of stable and immunogenic mRNA vaccines. Methods Mol. Biol. 1499 , 89–107 (2017).

Edwards, D. K. et al. Adjuvant effects of a sequence-engineered mRNA vaccine: translational profiling demonstrates similar human and murine innate response. J. Transl Med. 15 , 1 (2017).

Kowalczyk, A. et al. Self-adjuvanted mRNA vaccines induce local innate immune responses that lead to a potent and boostable adaptive immunity. Vaccine 34 , 3882–3893 (2016).

Schnee, M. et al. An mRNA vaccine encoding rabies virus glycoprotein induces protection against lethal infection in mice and correlates of protection in adult and newborn pigs. PLoS Negl. Trop. Dis. 10 , e0004746 (2016).

Ziegler, A. et al. A new RNA-based adjuvant enhances virus-specific vaccine responses by locally triggering TLR- and RLH-dependent effects. J. Immunol. 198 , 1595–1605 (2017).

Benteyn, D., Heirman, C., Bonehill, A., Thielemans, K. & Breckpot, K. mRNA-based dendritic cell vaccines. Expert Rev. Vaccines 14 , 161–176 (2015).

Kranz, L. M. et al. Systemic RNA delivery to dendritic cells exploits antiviral defence for cancer immunotherapy. Nature 534 , 396–401 (2016).

Wykes, M., Pombo, A., Jenkins, C. & MacPherson, G. G. Dendritic cells interact directly with naive B lymphocytes to transfer antigen and initiate class switching in a primary T-dependent response. J. Immunol. 161 , 1313–1319 (1998).

CAS   PubMed   Google Scholar  

Selmi, A. et al. Uptake of synthetic naked RNA by skin-resident dendritic cells via macropinocytosis allows antigen expression and induction of T-cell responses in mice. Cancer Immunol. Immunother. 65 , 1075–1083 (2016).

Diken, M. et al. Selective uptake of naked vaccine RNA by dendritic cells is driven by macropinocytosis and abrogated upon DC maturation. Gene Ther. 18 , 702–708 (2011).

Lorenz, C. et al. Protein expression from exogenous mRNA: uptake by receptor-mediated endocytosis and trafficking via the lysosomal pathway. RNA Biol. 8 , 627–636 (2011).

Gehl, J. Electroporation: theory and methods, perspectives for drug delivery, gene therapy and research. Acta Physiol. Scand. 177 , 437–447 (2003).

Granstein, R. D., Ding, W. & Ozawa, H. Induction of anti-tumor immunity with epidermal cells pulsed with tumor-derived RNA or intradermal administration of RNA. J. Invest. Dermatol. 114 , 632–636 (2000).

Kreiter, S. et al. Intranodal vaccination with naked antigen-encoding RNA elicits potent prophylactic and therapeutic antitumoral immunity. Cancer Res. 70 , 9031–9040 (2010).

Bialkowski, L. et al. Intralymphatic mRNA vaccine induces CD8 T-cell responses that inhibit the growth of mucosally located tumours. Sci. Rep. 6 , 22509 (2016).

Sahin, U. et al. Personalized RNA mutanome vaccines mobilize poly-specific therapeutic immunity against cancer. Nature 547 , 222–226 (2017).

Qiu, P., Ziegelhoffer, P., Sun, J. & Yang, N. S. Gene gun delivery of mRNA in situ results in efficient transgene expression and genetic immunization. Gene Ther. 3 , 262–268 (1996).

Steitz, J., Britten, C. M., Wolfel, T. & Tuting, T. Effective induction of anti-melanoma immunity following genetic vaccination with synthetic mRNA coding for the fusion protein EGFP.TRP2. Cancer Immunol. Immunother. 55 , 246–253 (2006).

Aberle, J. H., Aberle, S. W., Kofler, R. M. & Mandl, C. W. Humoral and cellular immune response to RNA immunization with flavivirus replicons derived from tick-borne encephalitis virus. J. Virol. 79 , 15107–15113 (2005).

Kofler, R. M. et al. Mimicking live flavivirus immunization with a noninfectious RNA vaccine. Proc. Natl Acad. Sci. USA 101 , 1951–1956 (2004).

Mandl, C. W. et al. In vitro -synthesized infectious RNA as an attenuated live vaccine in a flavivirus model. Nat. Med. 4 , 1438–1440 (1998).

Johansson, D. X., Ljungberg, K., Kakoulidou, M. & Liljestrom, P. Intradermal electroporation of naked replicon RNA elicits strong immune responses. PLoS ONE 7 , e29732 (2012).

Piggott, J. M., Sheahan, B. J., Soden, D. M., O'Sullivan, G. C. & Atkins, G. J. Electroporation of RNA stimulates immunity to an encoded reporter gene in mice. Mol. Med. Rep. 2 , 753–756 (2009).

Broderick, K. E. & Humeau, L. M. Electroporation-enhanced delivery of nucleic acid vaccines. Expert Rev. Vaccines 14 , 195–204 (2015).

Hoerr, I., Obst, R., Rammensee, H. G. & Jung, G. In vivo application of RNA leads to induction of specific cytotoxic T lymphocytes and antibodies. Eur. J. Immunol. 30 , 1–7 (2000).

Schlake, T., Thess, A., Fotin-Mleczek, M. & Kallen, K. J. Developing mRNA-vaccine technologies. RNA Biol. 9 , 1319–1330 (2012).

Reichmuth, A. M., Oberli, M. A., Jeklenec, A., Langer, R. & Blankschtein, D. mRNA vaccine delivery using lipid nanoparticles. Ther. Deliv. 7 , 319–334 (2016).

Midoux, P. & Pichon, C. Lipid-based mRNA vaccine delivery systems. Expert Rev. Vaccines 14 , 221–234 (2015).

Kanasty, R., Dorkin, J. R., Vegas, A. & Anderson, D. Delivery materials for siRNA therapeutics. Nat. Mater. 12 , 967–977 (2013).

Akinc, A. et al. Targeted delivery of RNAi therapeutics with endogenous and exogenous ligand-based mechanisms. Mol. Ther. 18 , 1357–1364 (2010).

Ratajczak, M. Z. & Ratajczak, J. Horizontal transfer of RNA and proteins between cells by extracellular microvesicles: 14 years later. Clin. Transl Med. 5 , 7 (2016).

PubMed Central   PubMed   Google Scholar  

Tam, H. H. et al. Sustained antigen availability during germinal center initiation enhances antibody responses to vaccination. Proc. Natl Acad. Sci. USA 113 , E6639–E6648 (2016).

Richner, J. M. et al. Modified mRNA Vaccines protect against Zika virus infection. Cell 168 , 1114–1125.e10 (2017).

Havenar-Daughton, C., Lee, J. H. & Crotty, S. Tfh cells and HIV bnAbs, an immunodominance model of the HIV neutralizing antibody generation problem. Immunol. Rev. 275 , 49–61 (2017).

Brito, L. A. et al. Self-amplifying mRNA vaccines. Adv. Genet. 89 , 179–233 (2015).

Chahal, J. S. et al. An RNA nanoparticle vaccine against Zika virus elicits antibody and CD8 + T cell responses in a mouse model. Sci. Rep. 7 , 252 (2017).

Chahal, J. S. et al. Dendrimer-RNA nanoparticles generate protective immunity against lethal Ebola, H1N1 influenza, and Toxoplasma gondii challenges with a single dose. Proc. Natl Acad. Sci. USA 113 , E4133–E4142 (2016).

Ulmer, J. B. & Geall, A. J. Recent innovations in mRNA vaccines. Curr. Opin. Immunol. 41 , 18–22 (2016).

Alberer, M. et al. Safety and immunogenicity of a mRNA rabies vaccine in healthy adults: an open-label, non-randomised, prospective, first-in-human phase 1 clinical trial. Lancet 390 , 1511–1520 (2017). This is a report of a clinical vaccine trial using directly injected, non-replicating, unmodified mRNA against an infectious pathogen.

Perri, S. et al. An alphavirus replicon particle chimera derived from venezuelan equine encephalitis and sindbis viruses is a potent gene-based vaccine delivery vector. J. Virol. 77 , 10394–10403 (2003).

Fleeton, M. N. et al. Self-replicative RNA vaccines elicit protection against influenza A virus, respiratory syncytial virus, and a tickborne encephalitis virus. J. Infect. Dis. 183 , 1395–1398 (2001). This is an early report of the protective efficacy that results from self-amplifying mRNA vaccines against infectious pathogens.

Magini, D. et al. Self-amplifying mRNA vaccines expressing multiple conserved influenza antigens confer protection against homologous and heterosubtypic viral challenge. PLoS ONE 11 , e0161193 (2016).

Hekele, A. et al. Rapidly produced SAM ® vaccine against H7N9 influenza is immunogenic in mice. Emerg. Microbes Infect. 2 , e52 (2013).

Brazzoli, M. et al. Induction of broad-based immunity and protective efficacy by self-amplifying mRNA vaccines encoding influenza virus hemagglutinin. J. Virol. 90 , 332–344 (2015).

Bogers, W. M. et al. Potent immune responses in rhesus macaques induced by nonviral delivery of a self-amplifying RNA vaccine expressing HIV type 1 envelope with a cationic nanoemulsion. J. Infect. Dis. 211 , 947–955 (2015).

McCullough, K. C. et al. Self-replicating replicon-RNA delivery to dendritic cells by chitosan-nanoparticles for translation in vitro and in vivo . Mol. Ther. Nucleic Acids 3 , e173 (2014).

Demoulins, T. et al. Polyethylenimine-based polyplex delivery of self-replicating RNA vaccines. Nanomedicine 12 , 711–722 (2016).

Maruggi, G. et al. Immunogenicity and protective efficacy induced by self-amplifying mRNA vaccines encoding bacterial antigens. Vaccine 35 , 361–368 (2017).

Van Gulck, E. et al. mRNA-based dendritic cell vaccination induces potent antiviral T-cell responses in HIV-1-infected patients. AIDS 26 , F1–F12 (2012).

Routy, J. P. et al. Immunologic activity and safety of autologous HIV RNA-electroporated dendritic cells in HIV-1 infected patients receiving antiretroviral therapy. Clin. Immunol. 134 , 140–147 (2010).

Allard, S. D. et al. A phase I/IIa immunotherapy trial of HIV-1-infected patients with Tat, Rev and Nef expressing dendritic cells followed by treatment interruption. Clin. Immunol. 142 , 252–268 (2012).

Gandhi, R. T. et al. Immunization of HIV-1-infected persons with autologous dendritic cells transfected with mRNA encoding HIV-1 Gag and Nef: results of a randomized, placebo-controlled clinical trial. J. Acquir. Immune Def. Syndr. 71 , 246–253 (2016).

Article   CAS   Google Scholar  

Jacobson, J. M. et al. Dendritic cell immunotherapy for HIV-1 infection using autologous HIV-1 RNA: a randomized, double-blind, placebo-controlled clinical trial. J. Acquir. Immune Def. Syndr. 72 , 31–38 (2016).

Gay, C. L. et al. Immunogenicity of AGS-004 dendritic cell therapy in patients treated during acute HIV infection. AIDS Res. Hum. Retroviruses 10.1089/aid.2017.0071 (2017).

Van Craenenbroeck, A. H. et al. Induction of cytomegalovirus-specific T cell responses in healthy volunteers and allogeneic stem cell recipients using vaccination with messenger RNA-transfected dendritic cells. Transplantation 99 , 120–127 (2015).

Martinon, F. et al. Induction of virus-specific cytotoxic T lymphocytes in vivo by liposome-entrapped mRNA. Eur. J. Immunol. 23 , 1719–1722 (1993). This early study demonstrates that liposome-encapsulated mRNA encoding a viral antigen induces T cell responses.

Pollard, C. et al. Type I IFN counteracts the induction of antigen-specific immune responses by lipid-based delivery of mRNA vaccines. Mol. Ther. 21 , 251–259 (2013).

Zhao, M., Li, M., Zhang, Z., Gong, T. & Sun, X. Induction of HIV-1 gag specific immune responses by cationic micelles mediated delivery of gag mRNA. Drug Deliv. 23 , 2596–2607 (2016).

Li, M. et al. Enhanced intranasal delivery of mRNA vaccine by overcoming the nasal epithelial barrier via intra- and paracellular pathways. J. Control. Release 228 , 9–19 (2016).

Richner, J. M. et al. Vaccine mediated protection against Zika virus-induced congenital disease. Cell 170 , 273–283.e12 (2017).

Roman, F., Vaman, T., Kafeja, F., Hanon, E. & Van Damme, P. AS03(A)-adjuvanted influenza A (H1N1) 2009 vaccine for adults up to 85 years of age. Clin. Infect. Dis. 51 , 668–677 (2010).

Zarei, S. et al. Immunogenicity and reactogenicity of two diphtheria-tetanus-whole cell pertussis vaccines in Iranian pre-school children, a randomized controlled trial. Hum. Vaccin. Immunother. 9 , 1316–1322 (2013).

Diken, M., Kranz, L. M., Kreiter, S. & Sahin, U. mRNA: a versatile molecule for cancer vaccines. Curr. Issues Mol. Biol. 22 , 113–128 (2017).

Fiedler, K., Lazzaro, S., Lutz, J., Rauch, S. & Heidenreich, R. mRNA cancer vaccines. Recent Results Cancer Res. 209 , 61–85 (2016).

Grunwitz, C. & Kranz, L. M. mRNA cancer vaccines-messages that prevail. Curr. Top. Microbiol. Immunol. 405 , 145–164 (2017).

McNamara, M. A., Nair, S. K. & Holl, E. K. RNA-Based Vaccines in Cancer Immunotherapy. J. Immunol. Res. 2015 , 794528 (2015).

Sullenger, B. A. & Nair, S. From the RNA world to the clinic. Science 352 , 1417–1420 (2016).

Vigneron, N. Human tumor antigens and cancer immunotherapy. Biomed. Res. Int. 2015 , 948501 (2015).

Tureci, O. et al. Targeting the heterogeneity of cancer with individualized neoepitope vaccines. Clin. Cancer Res. 22 , 1885–1896 (2016).

Coulie, P. G., Van den Eynde, B. J., van der Bruggen, P. & Boon, T. Tumour antigens recognized by T lymphocytes: at the core of cancer immunotherapy. Nat. Rev. Cancer 14 , 135–146 (2014).

Conry, R. M. et al. Characterization of a messenger RNA polynucleotide vaccine vector. Cancer Res. 55 , 1397–1400 (1995).

Boczkowski, D., Nair, S. K., Snyder, D. & Gilboa, E. Dendritic cells pulsed with RNA are potent antigen-presenting cells in vitro and in vivo . J. Exp. Med. 184 , 465–472 (1996). This report demonstrates the efficacy of mRNA DC vaccines.

De Keersmaecker, B. et al. The combination of 4-1BBL and CD40L strongly enhances the capacity of dendritic cells to stimulate HIV-specific T cell responses. J. Leukoc. Biol. 89 , 989–999 (2011).

Dannull, J. et al. Enhancing the immunostimulatory function of dendritic cells by transfection with mRNA encoding OX40 ligand. Blood 105 , 3206–3213 (2005).

Aerts-Toegaert, C. et al. CD83 expression on dendritic cells and T cells: correlation with effective immune responses. Eur. J. Immunol. 37 , 686–695 (2007).

Grunebach, F. et al. Cotransfection of dendritic cells with RNA coding for HER-2/neu and 4-1BBL increases the induction of tumor antigen specific cytotoxic T lymphocytes. Cancer Gene Ther. 12 , 749–756 (2005).

Bontkes, H. J., Kramer, D., Ruizendaal, J. J., Meijer, C. J. & Hooijberg, E. Tumor associated antigen and interleukin-12 mRNA transfected dendritic cells enhance effector function of natural killer cells and antigen specific T-cells. Clin. Immunol. 127 , 375–384 (2008).

Bontkes, H. J. et al. Dendritic cells transfected with interleukin-12 and tumor-associated antigen messenger RNA induce high avidity cytotoxic T cells. Gene Ther. 14 , 366–375 (2007).

Dorrie, J. et al. Introduction of functional chimeric E/L-selectin by RNA electroporation to target dendritic cells from blood to lymph nodes. Cancer Immunol. Immunother. 57 , 467–477 (2008).

Bonehill, A. et al. Enhancing the T-cell stimulatory capacity of human dendritic cells by co-electroporation with CD40L, CD70 and constitutively active TLR4 encoding mRNA. Mol. Ther. 16 , 1170–1180 (2008). This is a description of the TriMix mRNA adjuvant cocktail.

Van Lint, S. et al. Preclinical evaluation of TriMix and antigen mRNA-based antitumor therapy. Cancer Res. 72 , 1661–1671 (2012).

Van Lint, S. et al. Optimized dendritic cell-based immunotherapy for melanoma: the TriMix-formula. Cancer Immunol. Immunother. 63 , 959–967 (2014).

Pen, J. J. et al. Modulation of regulatory T cell function by monocyte-derived dendritic cells matured through electroporation with mRNA encoding CD40 ligand, constitutively active TLR4, and CD70. J. Immunol. 191 , 1976–1983 (2013).

Wilgenhof, S. et al. Therapeutic vaccination with an autologous mRNA electroporated dendritic cell vaccine in patients with advanced melanoma. J. Immunother. 34 , 448–456 (2011).

Wilgenhof, S. et al. A phase IB study on intravenous synthetic mRNA electroporated dendritic cell immunotherapy in pretreated advanced melanoma patients. Ann. Oncol. 24 , 2686–2693 (2013).

Mitchell, D. A. et al. Tetanus toxoid and CCL3 improve dendritic cell vaccines in mice and glioblastoma patients. Nature 519 , 366–369 (2015).

Batich, K. A. et al. Long-term survival in glioblastoma with cytomegalovirus pp65-targeted vaccination. Clin. Cancer Res. 23 , 1898–1909 (2017).

Wilgenhof, S. et al. Phase II study of autologous monocyte-derived mRNA electroporated dendritic cells (TriMixDC-MEL) plus ipilimumab in patients with pretreated advanced melanoma. J. Clin. Oncol. 34 , 1330–1338 (2016).

Zhou, W. Z. et al. RNA melanoma vaccine: induction of antitumor immunity by human glycoprotein 100 mRNA immunization. Hum. Gene Ther. 10 , 2719–2724 (1999).

Kreiter, S. et al. FLT3 ligand as a molecular adjuvant for naked RNA vaccines. Methods Mol. Biol. 1428 , 163–175 (2016).

Kreiter, S. et al. FLT3 ligand enhances the cancer therapeutic potency of naked RNA vaccines. Cancer Res. 71 , 6132–6142 (2011).

Bol, K. F. et al. Intranodal vaccination with mRNA-optimized dendritic cells in metastatic melanoma patients. Oncoimmunology 4 , e1019197 (2015).

Phua, K. K., Staats, H. F., Leong, K. W. & Nair, S. K. Intranasal mRNA nanoparticle vaccination induces prophylactic and therapeutic anti-tumor immunity. Sci. Rep. 4 , 5128 (2014).

Scheel, B. et al. Therapeutic anti-tumor immunity triggered by injections of immunostimulating single-stranded RNA. Eur. J. Immunol. 36 , 2807–2816 (2006).

Van der Jeught, K. et al. Intratumoral administration of mRNA encoding a fusokine consisting of IFN-β and the ectodomain of the TGF-β receptor II potentiates antitumor immunity. Oncotarget 5 , 10100–10113 (2014).

Van Lint, S. et al. Intratumoral delivery of TriMix mRNA results in T-cell activation by cross-presenting dendritic cells. Cancer Immunol. Res. 4 , 146–156 (2016).

Clausen, B. E. & Stoitzner, P. Functional specialization of skin dendritic cell subsets in regulating T Cell responses. Front. Immunol. 6 , 534 (2015).

Weide, B. et al. Direct injection of protamine-protected mRNA: results of a phase 1/2 vaccination trial in metastatic melanoma patients. J. Immunother. 32 , 498–507 (2009).

Kubler, H. et al. Self-adjuvanted mRNA vaccination in advanced prostate cancer patients: a first-in-man phase I/IIa study. J. Immunother. Cancer 3 , 26 (2015).

Hess, P. R., Boczkowski, D., Nair, S. K., Snyder, D. & Gilboa, E. Vaccination with mRNAs encoding tumor-associated antigens and granulocyte-macrophage colony-stimulating factor efficiently primes CTL responses, but is insufficient to overcome tolerance to a model tumor/self antigen. Cancer Immunol. Immunother. 55 , 672–683 (2006).

Oberli, M. A. et al. Lipid nanoparticle assisted mRNA delivery for potent cancer immunotherapy. Nano Lett. 17 , 1326–1335 (2017).

Fotin-Mleczek, M. et al. Highly potent mRNA based cancer vaccines represent an attractive platform for combination therapies supporting an improved therapeutic effect. J. Gene Med. 14 , 428–439 (2012).

Fotin-Mleczek, M. et al. mRNA-based vaccines synergize with radiation therapy to eradicate established tumors. Radiat. Oncol. 9 , 180 (2014).

Pascolo, S. Messenger RNA-based vaccines. Expert Opin. Biol. Ther. 4 , 1285–1294 (2004).

Geall, A. J., Mandl, C. W. & Ulmer, J. B. RNA: the new revolution in nucleic acid vaccines. Semin. Immunol. 25 , 152–159 (2013).

Weissman, D., Pardi, N., Muramatsu, H. & Kariko, K. HPLC purification of in vitro transcribed long RNA. Methods Mol. Biol. 969 , 43–54 (2013).

Muralidhara, B. K. et al. Critical considerations for developing nucleic acid macromolecule based drug products. Drug Discov. Today 21 , 430–444 (2016).

Jones, K. L., Drane, D. & Gowans, E. J. Long-term storage of DNA-free RNA for use in vaccine studies. Biotechniques 43 , 675–681 (2007).

Probst, J. et al. Characterization of the ribonuclease activity on the skin surface. Genet. Vaccines Ther. 4 , 4 (2006).

U.S. Food & Drug Administration. Guidance for Industry: Considerations for plasmid DNA vaccines for infectious disease indications. U.S. Food & Drug Administration https://www.fda.gov/downloads/BiologicsBloodVaccines/GuidanceComplianceRegulatoryInformation/Guidances/Vaccines/ucm091968.pdf (2007).

U.S. Food & Drug Administration. Guidance for Industry: Guidance for human somatic cell therapy and gene therapy. U.S. Food & Drug Administration https://www.fda.gov/downloads/BiologicsBloodVaccines/GuidanceComplianceRegulatoryInformation/Guidances/CellularandGeneTherapy/ucm081670.pdf (1998).

European Medicines Agency. Commission Directive 2009/120/EC. European Commission https://ec.europa.eu/health//sites/health/files/files/eudralex/vol-1/dir_2009_120/dir_2009_120_en.pdf (2009).

Hinz, T. et al. The European regulatory environment of RNA-based vaccines. Methods Mol. Biol. 1499 , 203–222 (2017).

Pepini, T. et al. Induction of an IFN-mediated antiviral response by a self-amplifying RNA vaccine: implications for vaccine design. J. Immunol. 198 , 4012–4024 (2017).

Theofilopoulos, A. N., Baccala, R., Beutler, B. & Kono, D. H. Type I interferons (α/β) in immunity and autoimmunity. Annu. Rev. Immunol. 23 , 307–336 (2005).

Nestle, F. O. et al. Plasmacytoid predendritic cells initiate psoriasis through interferon-α production. J. Exp. Med. 202 , 135–143 (2005).

Fischer, S. et al. Extracellular RNA mediates endothelial-cell permeability via vascular endothelial growth factor. Blood 110 , 2457–2465 (2007).

Kannemeier, C. et al. Extracellular RNA constitutes a natural procoagulant cofactor in blood coagulation. Proc. Natl Acad. Sci. USA 104 , 6388–6393 (2007).

Liu, M. A. & Ulmer, J. B. Human clinical trials of plasmid DNA vaccines. Adv. Genet. 55 , 25–40 (2005).

DeFrancesco, L. The 'anti-hype' vaccine. Nat. Biotechnol. 35 , 193–197 (2017).

Servick, K. On message. Science 355 , 446–450 (2017).

CureVac AG. From science to patients — ideas become treatments at CureVac. CureVac http://www.curevac.com/research-development (2017).

Aldevron. Aldevron expands North Dakota biomanufacturing facility. Aldevron http://www.aldevron.com/about-us/news/aldevron-expands-north-dakota-biomanufacturing-facility (2016).

Kreiter, S. et al. Mutant MHC class II epitopes drive therapeutic immune responses to cancer. Nature 520 , 692–696 (2015).

Ott, P. A. et al. An immunogenic personal neoantigen vaccine for patients with melanoma. Nature 547 , 217–221 (2017).

Jacobson, E. B., Caporale, L. H. & Thorbecke, G. J. Effect of thymus cell injections on germinal center formation in lymphoid tissues of nude (thymusless) mice. Cell. Immunol. 13 , 416–430 (1974).

Forster, R., Emrich, T., Kremmer, E. & Lipp, M. Expression of the G-protein-coupled receptor BLR1 defines mature, recirculating B cells and a subset of T-helper memory cells. Blood 84 , 830–840 (1994).

Forster, R. et al. A putative chemokine receptor, BLR1, directs B cell migration to defined lymphoid organs and specific anatomic compartments of the spleen. Cell 87 , 1037–1047 (1996).

Breitfeld, D. et al. Follicular B helper T cells express CXC chemokine receptor 5, localize to B cell follicles, and support immunoglobulin production. J. Exp. Med. 192 , 1545–1552 (2000).

Schaerli, P. et al. CXC chemokine receptor 5 expression defines follicular homing T cells with B cell helper function. J. Exp. Med. 192 , 1553–1562 (2000).

Johnston, R. J. et al. Bcl6 and Blimp-1 are reciprocal and antagonistic regulators of T follicular helper cell differentiation. Science 325 , 1006–1010 (2009).

Nurieva, R. I. et al. Bcl6 mediates the development of T follicular helper cells. Science 325 , 1001–1005 (2009).

Yu, D. et al. The transcriptional repressor Bcl-6 directs T follicular helper cell lineage commitment. Immunity 31 , 457–468 (2009).

Crotty, S. A brief history of T cell help to B cells. Nat. Rev. Immunol. 15 , 185–189 (2015).

Klein, F. et al. Antibodies in HIV-1 vaccine development and therapy. Science 341 , 1199–1204 (2013).

Gils, A., Bertolotto, A., Mulleman, D., Bejan-Angoulvant, T. & Declerck, P. J. Biopharmaceuticals: reference products and biosimilars to treat inflammatory diseases. Ther. Drug Monit. 39 , 308–315 (2017).

Sparrow, E., Friede, M., Sheikh, M. & Torvaldsen, S. Therapeutic antibodies for infectious diseases. Bull. World Health Organ. 95 , 235–237 (2017).

Henricks, L. M., Schellens, J. H., Huitema, A. D. & Beijnen, J. H. The use of combinations of monoclonal antibodies in clinical oncology. Cancer Treat. Rev. 41 , 859–867 (2015).

Lewiecki, E. M. Treatment of osteoporosis with denosumab. Maturitas 66 , 182–186 (2010).

Paton, D. M. PCSK9 inhibitors: monoclonal antibodies for the treatment of hypercholesterolemia. Drugs Today 52 , 183–192 (2016).

Hollevoet, K. & Declerck, P. J. State of play and clinical prospects of antibody gene transfer. J. Transl Med. 15 , 131 (2017).

Fuchs, S. P. & Desrosiers, R. C. Promise and problems associated with the use of recombinant AAV for the delivery of anti-HIV antibodies. Mol. Ther. Methods Clin. Dev. 3 , 16068 (2016).

Boczkowski, D., Lee, J., Pruitt, S. & Nair, S. Dendritic cells engineered to secrete anti-GITR antibodies are effective adjuvants to dendritic cell-based immuno-therapy. Cancer Gene Ther. 16 , 900–911 (2009).

Pruitt, S. K. et al. Enhancement of anti-tumor immunity through local modulation of CTLA-4 and GITR by dendritic cells. Eur. J. Immunol. 41 , 3553–3563 (2011).

Pardi, N. et al. Administration of nucleoside-modified mRNA encoding broadly neutralizing antibody protects humanized mice from HIV-1 challenge. Nat. Commun. 8 , 14630 (2017). This is the first study to demonstrate that directly injected, non-replicating mRNA encoding a monoclonal antibody protects animals against an infectious pathogen.

Stadler, C. R. et al. Elimination of large tumors in mice by mRNA-encoded bispecific antibodies. Nat. Med. 23 , 815–817 (2017).

Thran, M. et al. mRNA mediates passive vaccination against infectious agents, toxins, and tumors. EMBO Mol. Med. 9 , 1434–1447 (2017).

Sebastian, M. et al. Phase Ib study evaluating a self-adjuvanted mRNA cancer vaccine (RNActive ® ) combined with local radiation as consolidation and maintenance treatment for patients with stage IV non-small cell lung cancer. BMC Cancer 14 , 748 (2014).

Wang, Y. et al. Systemic delivery of modified mRNA encoding herpes simplex virus 1 thymidine kinase for targeted cancer gene therapy. Mol. Ther. 21 , 358–367 (2013).

Perche, F. et al. Enhancement of dendritic cells transfection in vivo and of vaccination against B16F10 melanoma with mannosylated histidylated lipopolyplexes loaded with tumor antigen messenger RNA. Nanomedicine 7 , 445–453 (2011).

Mockey, M. et al. mRNA-based cancer vaccine: prevention of B16 melanoma progression and metastasis by systemic injection of MART1 mRNA histidylated lipopolyplexes. Cancer Gene Ther. 14 , 802–814 (2007).

Uchida, S. et al. Systemic delivery of messenger RNA for the treatment of pancreatic cancer using polyplex nanomicelles with a cholesterol moiety. Biomaterials 82 , 221–228 (2016).

Lazzaro, S. et al. CD8 T-cell priming upon mRNA vaccination is restricted to bone-marrow-derived antigen-presenting cells and may involve antigen transfer from myocytes. Immunology 146 , 312–326 (2015).

Van Driessche, A. et al. Clinical-grade manufacturing of autologous mature mRNA-electroporated dendritic cells and safety testing in acute myeloid leukemia patients in a phase I dose-escalation clinical trial. Cytotherapy 11 , 653–668 (2009).

Van Tendeloo, V. F. et al. Induction of complete and molecular remissions in acute myeloid leukemia by Wilms' tumor 1 antigen-targeted dendritic cell vaccination. Proc. Natl Acad. Sci. USA 107 , 13824–13829 (2010).

Berneman, Z. N. et al. Dendritic cell vaccination in malignant pleural mesothelioma: a phase I/II study [abstract]. J. Clin. Oncol. 32 (Suppl.), 7583 (2014).

Article   Google Scholar  

Amin, A. et al. Survival with AGS-003, an autologous dendritic cell-based immunotherapy, in combination with sunitinib in unfavorable risk patients with advanced renal cell carcinoma (RCC): phase 2 study results. J. Immunother. Cancer 3 , 14 (2015).

Khoury, H. J. et al. Immune responses and long-term disease recurrence status after telomerase-based dendritic cell immunotherapy in patients with acute myeloid leukemia. Cancer 123 , 3061–3072 (2017).

Sebastian, M. et al. Messenger RNA vaccination in NSCLC: findings from a phase I/IIa clinical trial [abstract]. J. Clin. Oncol. 29 (Suppl.), 2584 (2011).

Rausch, S., Schwentner, C., Stenzl, A. & Bedke, J. mRNA vaccine CV9103 and CV9104 for the treatment of prostate cancer. Hum. Vaccin Immunother. 10 , 3146–3152 (2014).

Mitchell, D. A. et al. Monoclonal antibody blockade of IL-2 receptor α during lymphopenia selectively depletes regulatory T cells in mice and humans. Blood 118 , 3003–3012 (2011).

Borch, T. H. et al. mRNA-transfected dendritic cell vaccine in combination with metronomic cyclophosphamide as treatment for patients with advanced malignant melanoma. Oncoimmunology 5 , e1207842 (2016).

Kongsted, P. et al. Dendritic cell vaccination in combination with docetaxel for patients with metastatic castration-resistant prostate cancer: a randomized phase II study. Cytotherapy 19 , 500–513 (2017).

Kyte, J. A. et al. Immune response and long-term clinical outcome in advanced melanoma patients vaccinated with tumor-mRNA-transfected dendritic cells. Oncoimmunology 5 , e1232237 (2016).

Vik-Mo, E. O. et al. Therapeutic vaccination against autologous cancer stem cells with mRNA-transfected dendritic cells in patients with glioblastoma. Cancer Immunol. Immunother. 62 , 1499–1509 (2013).

Lesterhuis, W. J. et al. Immunogenicity of dendritic cells pulsed with CEA peptide or transfected with CEA mRNA for vaccination of colorectal cancer patients. Anticancer Res. 30 , 5091–5097 (2010).

PubMed   Google Scholar  

Aarntzen, E. H. et al. Vaccination with mRNA-electroporated dendritic cells induces robust tumor antigen-specific CD4 + and CD8 + T cells responses in stage III and IV melanoma patients. Clin. Cancer Res. 18 , 5460–5470 (2012).

Bol, K. F. et al. Long overall survival after dendritic cell vaccination in metastatic uveal melanoma patients. Am. J. Ophthalmol. 158 , 939–947 (2014).

Bol, K. F. et al. Prophylactic vaccines are potent activators of monocyte-derived dendritic cells and drive effective anti-tumor responses in melanoma patients at the cost of toxicity. Cancer Immunol. Immunother. 65 , 327–339 (2016).

Weide, B. et al. Results of the first phase I/II clinical vaccination trial with direct injection of mRNA. J. Immunother. 31 , 180–188 (2008).

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Acknowledgements

D.W. was supported by the National Institute of Allergy and Infectious Disease (NIAID) of the US National Institutes of Health (NIH) under award numbers CHAVI-ID UM1-AI100645, R01-AI050484, R01-AI124429 and R01-AI084860, by Gates Foundation Collaboration for AIDS Vaccine Discovery (CAVD) grant OPP1033102, by the Defense Advanced Research Projects Agency under grant HR0011-17-2-0069 and by the New Frontier Sciences division of Takeda Pharmaceuticals. F.W.P. was supported by the Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery (CHAVI-ID) grant UM1-AI100645, Defense Advanced Research Projects Agency grant HR0011-17-2-0069 and by Gates Foundation grant OPP1066832. The authors acknowledge K. Karikó for her profoundly helpful advice.

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Department of Medicine, University of Pennsylvania, Philadelphia, 19104, Pennsylvania, USA

Norbert Pardi, Michael J. Hogan & Drew Weissman

Duke Human Vaccine Institute, Duke University School of Medicine, Durham, 27710, North Carolina, USA

Frederick W. Porter

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Correspondence to Drew Weissman .

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Competing interests.

In accordance with the University of Pennsylvania policies and procedures and our ethical obligations as researchers, we report that Norbert Pardi, Michael J. Hogan and Drew Weissman are named on patents that describe the use of nucleoside-modified mRNA as a platform to deliver therapeutic proteins and vaccines. We have disclosed those interests fully to the University of Pennsylvania, and we have in place an approved plan for managing any potential conflicts arising from licensing of our patents. Frederick Porter reports no competing financial interests.

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Powerpoint slide for fig. 1, powerpoint slide for fig. 2, powerpoint slide for fig. 3, powerpoint slide for table 1, powerpoint slide for table 2, powerpoint slide for table 3, powerpoint slide for table 4.

(DC). A professional antigen-presenting cell that can potently activate CD4 + and CD8 + T cells by presenting peptide antigens on major histocompatibility complex (MHC) class I and II molecules, respectively, along with co-stimulatory molecules.

(PAMP). Conserved molecular structure produced by microorganisms and recognized as an inflammatory danger signal by various innate immune receptors.

A family of proteins, including but not limited to interferon-β (IFNβ) and multiple isoforms of IFNα, released by cells in response to viral infections and pathogen products. Type I IFN sensing results in the upregulation of interferon-stimulated genes and an antiviral cellular state.

(FPLC). A form of liquid chromatography that can be used to purify proteins or nucleic acids. High-performance liquid chromatography (HPLC) is a similar approach, which uses high pressure to purify materials.

The incorporation of chemically modified nucleosides, such as pseudouridine, 1-methylpseudouridine, 5-methylcytidine and others, into mRNA transcripts, usually to suppress innate immune sensing and/or to improve translation.

An additive to vaccines that modulates and/or boosts the potency of the immune response, often allowing lower doses of antigen to be used effectively. Adjuvants may be based on pathogen-associated molecular patterns (PAMPs) or on other molecules that activate innate immune sensors.

A polymorphic set of proteins expressed on the surface of all nucleated cells that present antigen to CD8 + (including cytotoxic) T cells in the form of proteolytically processed peptides, typically 8–11 amino acids in length.

A polymorphic set of proteins expressed on professional antigen-presenting cells and certain other cell types, which present antigen to CD4 + (helper) T cells in the form of proteolytically processed peptides, typically 11–30 amino acids in length.

(GMP). A collection of guidelines and practices designed to guarantee the production of consistently high-quality and safe pharmaceutical products. GMP-grade materials must be used for human clinical trials.

In contrast to traditional (active) vaccines, these therapies do not generate de novo immune responses but can provide immune-mediated protection through the delivery of antibodies or antibody-encoding genes. Passive vaccination offers the advantage of immediate action but at the disadvantage of high cost.

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Pardi, N., Hogan, M., Porter, F. et al. mRNA vaccines — a new era in vaccinology. Nat Rev Drug Discov 17 , 261–279 (2018). https://doi.org/10.1038/nrd.2017.243

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Published : 12 January 2018

Issue Date : April 2018

DOI : https://doi.org/10.1038/nrd.2017.243

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