Vaccine

From Jenner to mRNA

From around the 10th century, variolation — introducing a little material from smallpox sores — was practised in China, India and the Ottoman Empire, and Lady Mary Wortley Montagu promoted it in England from 1721. In 1796 the English physician Edward Jenner, noting that milkmaids who caught cowpox seemed protected from smallpox, inoculated a boy named James Phipps with cowpox and published his results in 1798. "Vaccine" comes from vacca, Latin for cow; in 1881 Louis Pasteur proposed extending the term to all such inoculations in Jenner's honour. Jonas Salk's inactivated polio vaccine (1955) and measles vaccines in the 1960s followed, and a WHO campaign eradicated smallpox, declared in 1980. In 2020 mRNA vaccines, built on Katalin Karikó and Drew Weissman's work, became COVID-19 vaccines in under a year.

How vaccines work and the main types

A vaccine shows the immune system a pathogen's "face" without real infection. B cells make antibodies, and T cells and memory cells form, so the body responds far faster and harder if the real pathogen arrives. When enough people are immune, chains of transmission break and even infants or patients who cannot be vaccinated are protected — herd immunity. Highly contagious diseases such as measles need about 95% coverage. Some vaccines, such as the HPV vaccine, prevent cancer by preventing infection.

Safety and myths

Most side effects — a sore arm, mild fever, tiredness — fade within a day or two. Severe allergic reactions such as anaphylaxis occur only a few times per million doses, which is why people are observed for 15–30 minutes after vaccination. Andrew Wakefield's 1998 paper linking the MMR vaccine to autism was found to be fraudulent and retracted by The Lancet in 2010, and studies of millions of children have repeatedly found no link. The WHO named "vaccine hesitancy" one of the top ten threats to global health in 2019. A 2024 Lancet analysis estimated that immunisation has saved about 154 million lives over the past 50 years. Check schedules and contraindications with your doctor or national health authority.

This article is general health information and is not a substitute for diagnosis or treatment. If symptoms persist, see a doctor.

FAQ

Can you still get sick after being vaccinated?

Yes. No vaccine is 100% effective, but vaccination greatly reduces the risk of severe illness and death. Some, like flu vaccines, must be updated yearly as circulating strains change.

Is it safe to get several vaccines at once?

For most vaccines, studies show co-administration is safe and does not reduce effectiveness. Some live vaccines need spacing, so follow your clinician's advice.

Sources reviewed: 2026-10-26

References

1. Jenner, E. (1798). An Inquiry into the Causes and Effects of the Variolae Vaccinae. London: Sampson Low.
2. Pasteur, L. (1880). De l'atténuation du virus du choléra des poules. Comptes Rendus de l'Académie des Sciences, 91, 673–680.
3. Salk, J. E. (1953). Studies in human subjects on active immunization against poliomyelitis. JAMA, 151(13), 1081–1098.
4. Fenner, F., Henderson, D. A., Arita, I., Ježek, Z., & Ladnyi, I. D. (1988). Smallpox and Its Eradication. Geneva: World Health Organization.
5. Plotkin, S. A. (2014). History of vaccination. PNAS, 111(34), 12283–12287.
6. Karikó, K., Buckstein, M., Ni, H., & Weissman, D. (2005). Suppression of RNA recognition by Toll-like receptors: The impact of nucleoside modification. Immunity, 23(2), 165–175.
7. Polack, F. P., et al. (2020). Safety and efficacy of the BNT162b2 mRNA Covid-19 vaccine. New England Journal of Medicine, 383(27), 2603–2615.
8. Taylor, B., Swerdfeger, A. L., & Eslick, G. D. (2014). Vaccines are not associated with autism: An evidence-based meta-analysis. Vaccine, 32(29), 3623–3629.
9. Shattock, A. J., et al. (2024). Contribution of vaccination to improved survival and health: Modelling 50 years of the Expanded Programme on Immunization. The Lancet, 403(10441), 2307–2316.