Billions of mRNA vaccine doses’ review underpins their effectiveness

Published on

30/06/2026 - 16:48 GMT+2

The mRNA vaccine — first deployed at scale during the COVID-19 pandemic — remains highly effective at preventing severe disease and serious adverse events remain rare, according to the review, published in The Lancet.

Unlike traditional vaccines, mRNA vaccines deliver genetic instructions that prompt cells to produce a harmless viral protein, training the immune system to recognise and fight infections without altering a person's DNA.

The scientific journal review found the vaccines were 87% effective against documented SARS-CoV-2 infection, 93% effective at preventing hospitalisation and 94% effective at preventing death within 14 to 42 days of vaccination. Protection declined over time, but booster doses restored much of the lost immunity.

Serious side effects, including myocarditis, pericarditis and anaphylaxis, were found to be very rare. Most reactions, such as sore arms, fatigue and fever, were mild to moderate and resolved within a few days.

"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," researchers said.

"Effectiveness has been shown across age groups, in pregnancy, and in populations that are immunocompromised, establishing mRNA vaccines as a clinically validated and adaptable platform"

Beyond infectious diseases, the researchers say the platform could underpin more personalised approaches to cancer treatment, with vaccines tailored to individual patients and tumour profiles.

"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," said co-author Manish Sadarangani of the University of British Columbia and BC Children's Hospital Research Institute.

Thanks to newer storage options, such as higher-temperature storage and freeze-drying, vaccines can reach remote places quickly and reduce waste.

But the researchers say scientific advances alone will not guarantee equitable access.

"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 co-author Robin Shattock of Imperial College London.

He said greater investment in technology transfer, local manufacturing and stronger regulatory systems would shorten supply chains, reduce costs and help ensure countries can access vaccines more quickly during future health emergencies.