A comprehensive review published in The Lancet affirms on June 30 that currently approved mRNA vaccines are safe and highly effective at preventing infectious diseases, including COVID-19. The review also highlights the potential of mRNA vaccine technologies for treating and preventing other health conditions such as influenza, RSV, cancer, and autoimmune disorders.
The authors analyzed published data from laboratory research, clinical trials, and real-world surveillance involving billions of doses. They assessed the science behind mRNA vaccines and their impact on public health. According to the review, serious adverse side effects from mRNA vaccines remain exceedingly rare. For example, real-world surveillance found incidents of myocarditis and pericarditis were higher among second-dose recipients: about 12.6 cases per million for Pfizer BioNTech's BNT162b2 vaccine and approximately 35.6 cases per million for Moderna's mRNA-1273 vaccine. However, the increased risk of these heart-related conditions following vaccination was significantly lower than the risk associated with a SARS-CoV-2 infection in males aged 12-19.
Other serious adverse events were also reported as very rare; anaphylaxis occurred at a rate of 4.7 cases per million doses (Pfizer), while Guillain-Barré Syndrome was observed at 38 cases per million doses (AstraZeneca). Most other side effects—such as sore arms, fatigue, or fever—were mild to moderate and resolved within a few days.
The analysis found that across clinical trials and real-world data sets, mRNA vaccines demonstrated approximately 87% effectiveness against any documented SARS-CoV-2 infection, 93% effectiveness against hospitalization, and 94% effectiveness against mortality within two to six weeks after vaccination. Effectiveness waned over time but could be restored with booster doses; it was also somewhat reduced by age or when facing Omicron variants (67% effective against infection; 72% against hospitalization). Ongoing monitoring continues to support the tolerability and efficacy of these vaccines as new variants emerge.
"Our comprehensive review provides compelling evidence confirming that approved mRNA vaccines are safe and highly effective. 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 lead study author Dr. Anna Blakney of the University of British Columbia.
Co-author Dr. Manish Sadarangani said, "As the world continues to confront evolving infectious threats, our review underscores the need for sustained innovation, robust surveillance, and true global collaboration to maximize the life-saving benefits of this groundbreaking technology...with ongoing innovation...they can drive progress in preventive medicine...for years to come." Co-author Dr. Robin Shattock emphasized expanding manufacturing capacity: "Expanding manufacturing capacity...is essential if mRNA vaccines are to fulfill their promise as a global public good...we can shorten supply chains, reduce costs, ensure people everywhere benefit from safe, effective vaccines beyond pandemics."
