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Vaccination (Jenner's smallpox vaccine)
May 14, 1796· Invention or discovery· Germs, drugs & genetics
Well documentedSolid records, physical evidence or scientific consensus.
Edward Jenner showed that infection with mild cowpox protected against smallpox, creating the first vaccine.
See it on the Technology & Medicine map →How it works
Country people in Gloucestershire believed milkmaids who caught cowpox were spared smallpox. On May 14, 1796, Jenner took matter from cowpox sores on milkmaid Sarah Nelmes's hand and inoculated James Phipps, aged eight. Weeks later he exposed Phipps to smallpox; the boy did not fall ill. Jenner published in 1798; the word 'vaccination' comes from vacca, Latin for cow. Within a decade vaccine was carried worldwide, including by Spain's Balmis expedition (1803–06).
Why it mattered
It was the first safe way to prevent a deadly disease, and it led directly to smallpox's eradication, declared in 1980.
How we know
Jenner's 1798 Inquiry, with 23 case histories, plus his letters and widespread trials. Farmer Benjamin Jesty had used cowpox on his family in 1774 but never published.
Still unknown or debated
The original vaccine's virus is unclear: modern genome studies suggest early vaccines descended from a horsepox-like virus rather than cowpox.
Inside this (1)
Connections (6)
▸Al-Razi (Rhazes) first distinguished the smallpox later prevented by Vaccination (Jenner's smallpox vaccine)Mostly agreed
The connection
Around 910, the Persian physician al-Razi wrote the first known clear account telling smallpox apart from measles, describing its signs and course. Clear diagnosis came before prevention: Jenner's vaccine, nine centuries later, targeted the same disease al-Razi had defined. The link runs through medical knowledge, not a direct step.
When and how
Baghdad and Rayy, near modern Tehran, around AD 900–925; his treatise was later translated into Latin and printed in Europe.
How sure are we?
His treatise On Smallpox and Measles survives and was widely translated and printed; there is no evidence Jenner relied on it directly.
Debates and open questions
Earlier texts from China (Ge Hong, 300s) and India may describe smallpox; who wrote the first account depends on how strictly they are read.
▸Variolation (smallpox inoculation) was replaced by safer Vaccination (Jenner's smallpox vaccine)Well documented
The connection
Variolation deliberately infected people with material from smallpox sores, usually causing a mild case and lifelong immunity, but it killed perhaps 1–2% and could spread smallpox. Jenner used cowpox, a mild cattle disease, instead. It protected with far less danger and could not start a smallpox outbreak. Britain banned variolation in 1840.
When and how
Variolation in China, India, Africa and the Ottoman Empire for centuries; Jenner in Berkeley, England, 1796; British ban, 1840.
How we know
Jenner was variolated as a boy and used variolation to test whether his vaccinated patients were immune, as his 1798 Inquiry records.
Debates and open questions
Variolation death rates are estimates and varied by method; how early variolation began in Asia and Africa is uncertain.
▸Vaccination (Jenner's smallpox vaccine) was generalised by Louis PasteurWell documented
The connection
Jenner's vaccine relied on a lucky natural cousin, cowpox. Pasteur found a general method: weaken the disease germ itself in the laboratory, by ageing cultures, heat or chemicals. He made vaccines for chicken cholera, anthrax and rabies, and proposed calling them all 'vaccines' in Jenner's honor.
When and how
Paris, 1879–85; public anthrax trial at Pouilly-le-Fort, May 1881; rabies treatment of Joseph Meister, July 1885.
How we know
Pasteur's 1881 papers, the press-covered Pouilly-le-Fort trial, and his explicit tribute to Jenner at the London medical congress of 1881.
Debates and open questions
Pasteur's notebooks show his anthrax vaccine was made by a chemical method like rival Toussaint's, not the oxygen method he described; credit to Toussaint and Roux is debated.
▸Vaccination (Jenner's smallpox vaccine) made possible Smallpox eradicationWell documented
The connection
Jenner's 1796 discovery that cowpox protects against smallpox gave the world a safe vaccine. Over 170 years it was improved into a freeze-dried, heat-stable vaccine given with a cheap two-pronged needle. The WHO campaign used it to vaccinate everyone around each new case until the virus had nowhere left to spread.
When and how
Jenner in Berkeley, Gloucestershire, England, 1796; the WHO's Intensified Eradication Programme, 1967–1977, led by D. A. Henderson, across South America, Africa and South Asia.
How we know
WHO records document vaccine supply, case-finding and the last cases. Eradication worked because smallpox has no animal host and the vaccine gives long-lasting protection.
Debates and open questions
Oddly, the virus in modern vaccine, vaccinia, is not cowpox; genetic studies suggest it may descend from horsepox, and when the switch happened is unknown.
▸Vaccination (Jenner's smallpox vaccine) was extended to Polio vaccines (Salk, Sabin)Well documented
The connection
Jenner showed in 1796 that a mild related infection, cowpox, could train the body to resist smallpox. Pasteur generalized the idea in the 1880s with weakened germs. Salk's killed-virus shot and Sabin's weakened live-virus drops applied the same principle to polio, once scientists could grow the virus in lab cultures.
When and how
Berkeley, England, 1796 (Jenner); Pasteur's lab in Paris, 1879–85; Pittsburgh (Salk) and Cincinnati (Sabin), 1950s.
How we know
The line of descent is documented in the scientists' own papers; Pasteur proposed extending the word 'vaccine', from Latin vacca (cow), to all such shots in Jenner's honor.
Debates and open questions
Smallpox fell to one vaccine partly because it showed obvious symptoms; polio has three types and spreads silently, one reason its eradication is still unfinished.
▸Vaccination (Jenner's smallpox vaccine) was reinvented, 224 years on, as mRNA vaccinesWell documented
The connection
Jenner's smallpox vaccine and mRNA vaccines share one principle: show the immune system a harmless version of a threat so it remembers. Jenner used cowpox; later vaccines used weakened or killed germs or purified proteins. mRNA vaccines instead give cells instructions to make the warning protein themselves, so they can be designed quickly from a genetic sequence.
When and how
Jenner in Berkeley, England, May 1796; BioNTech in Mainz, Germany, with Pfizer, and Moderna in Cambridge, Massachusetts, 2020.
How we know
The shared immune-memory principle is established immunology; the 224 years run from Jenner's 1796 test to the first mRNA vaccine authorization in December 2020.
Debates and open questions
Whether mRNA will replace traditional vaccines or stay one option among many is open; some older vaccines, such as measles, give longer-lasting protection.