mRNA vaccines safe and effective, confirms Lancet review
Drawing together evidence from laboratory research, clinical trials and real-world studies, the review also highlights the technology’s potential beyond COVID-19.
- 6 July 2026
- 6 min read
- by Linda Geddes
At a glance
- A comprehensive review of evidence from laboratory research, clinical trials and real-world studies has confirmed that mRNA-based vaccines are safe and effective, while highlighting their potential to prevent a growing number of infectious diseases, and treat other health conditions in the years to come.
- It concluded that serious adverse events were rare and substantially outweighed by protection against severe disease, hospitalisation and death.
- The authors called for continued safety monitoring and greater investment in manufacturing and technology transfer to ensure future mRNA technologies are accessible to all.
After more than two decades of research and billions of vaccine doses delivered, mRNA vaccines are firmly established as a safe and effective platform for preventing infectious disease.
That’s the conclusion of a comprehensive review published in The Lancet, which brought together findings from preclinical research, clinical trials and post-authorisation safety monitoring.
The authors found that serious adverse events were rare and substantially outweighed by protection against severe disease, hospitalisation and death.
They argue that the technology is poised to play an expanding role beyond COVID-19, including vaccines against influenza, RSV and other infectious diseases, personalised cancer vaccines, and other RNA-based therapies.
“As the world continues to confront evolving infectious threats, our review underscores the need for sustained innovation, robust surveillance and true global collaboration to maximise the life-saving benefits of this groundbreaking technology,” said study co-author Dr Manish Sadarangani of the University of British Columbia and BC Children’s Hospital Research Institute in Canada.
He added: “mRNA vaccines have already transformed how we respond to emerging diseases, and with ongoing innovation and rigorous safety monitoring, they can drive progress in preventive medicine and cancer treatment for years to come.”
How much do we now know about mRNA vaccines?
Although mRNA vaccines came to public awareness during the COVID-19 pandemic, the technology behind them had been under development for more than two decades.
They work by delivering genetic instructions that enable the body’s own cells to temporarily produce a target protein, such as the spike protein on the surface of SARS-CoV-2.
This trains the immune system to recognise and attack the protein, and pathogens carrying that protein, should it encounter it again.
To evaluate the science behind mRNA vaccines and their public health impact, Dr Anna Blakney at the University of British Columbia in Vancouver, Canada, and colleagues searched the scientific literature for studies published between 2000 and the end of 2025, as well as ongoing clinical trials.
Rather than focusing on a single vaccine or study, they evaluated the mRNA platform as a whole, drawing on data from laboratory research, clinical trials and real-world surveillance of billions of mRNA vaccine doses.
The researchers also examined several questions that have fuelled debate about mRNA vaccines since their widespread deployment during the COVID-19 pandemic, including how long vaccine mRNA persists in the body, whether it can integrate into human DNA and how its components are distributed and cleared.
How safe are mRNA vaccines?
The Lancet evidence suggests that both the mRNA and lipid nanoparticles that are injected into the body are temporary, remaining largely at the injection site and nearby lymph nodes, before being broken down.
mRNA does not enter the cell nucleus, where DNA is stored, while the vaccine-produced protein is expressed only transiently before being cleared from the body. These characteristics underpin the platform’s favourable safety profile, the authors said.
“Across billions of administered doses, serious adverse events have been rare, well characterised, and consistently outweighed by the substantial protection conferred against severe disease, hospitalisation, and death,” they wrote.
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For example, while incidents of myocarditis and pericarditis (heart-related inflammation) following vaccination have been observed during real-world surveillance, this was rare, with rates of roughly 12.6 cases per million for Pfizer BioNTech’s BNT162b2 vaccine and about 35.6 cases per million for Moderna’s mRNA-1273.
Importantly, the risk of these complications was significantly lower than the risk of myocarditis and pericarditis after catching SARS-CoV-2.
Other serious adverse events were also very rare. For example, the risk of anaphylaxis associated with the Pfizer BioNTech vaccine was 4.7 cases per million doses. Most other side effects, such as sore arms, fatigue, or fever, were mild to moderate and subsided after a few days.
Even so, the authors noted the importance of ongoing safety monitoring and long-term follow-up of rare adverse events, as well as clear and proactive communication of evidence to clinicians, policymakers and the public.
How effective are they?
mRNA vaccines have also proved highly effective in real-world use.
Initial clinical trials found that the first COVID-19 mRNA vaccines were more than 90% effective after two doses, while a later synthesis of 68 studies estimated that, in the first few weeks after vaccination, they reduced the risk of documented infection by 87%, hospitalisation by 93% and death by 94%.
Although protection against infection declined over time and with the emergence of new variants, booster doses helped restore it, while protection against severe disease remained high.
“Throughout the COVID-19 pandemic, mRNA vaccines demonstrated what rapid, science-driven collaboration can achieve by delivering safe, effective protection at an unprecedented scale.
“The key lessons from mRNA vaccine use during the COVID-19 pandemic are not only about manufacturing speed, but about the importance of sharing safety data, conducting ongoing rigorous real-world surveillance, and providing clear information about how new types of vaccines work and why they protect communities,” said Blakney.
What’s next for mRNA technology?
The success of COVID-19 vaccines has driven investment in mRNA vaccines against other infectious diseases.
Already, an mRNA-based vaccine against RSV has been approved for use in some countries, while vaccines against mpox, HIV, shingles, norovirus, seasonal influenza and tuberculosis are all in clinical trials.
Beyond infectious diseases, the authors point to growing interest in personalised cancer vaccines, which train the immune system to recognise tumour-specific proteins, and RNA-based medicines for rare inherited disorders.
However, they stressed that the technology was “not a panacea for all diseases”, citing the recent failure of an mRNA vaccine against congenital cytomegalovirus (a leading cause of childhood deafness) and that further advances will be needed to generate longer-lasting immune protection while reducing side-effects.
Ensuring global access to mRNA vaccines is another challenge.
“Early mRNA vaccines required ultra-cold storage, complicating distribution in low-resource settings,” the authors wrote. Although advances in formulation have made them more stable and easier to store and transport, production costs are still several times more than those of traditional vaccines.
“Expanding manufacturing capacity and ensuring equitable access in low- and middle-income countries is essential if mRNA vaccines are to fulfil their promise as a global public good,” said study co-author Prof Robin Shattock at Imperial College London, UK.
“By investing in technology transfer, local production and robust regulatory systems, we can shorten supply chains, reduce costs and ensure that people everywhere benefit from safe, effective vaccines beyond pandemics.”
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