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May-July 1796Reputable source · 2 sourcesWell documented

Edward Jenner Tests Cowpox Against Smallpox and Creates the First Vaccine

An English country doctor turns a dairymaid's folk belief into a repeatable medical procedure, decades before anyone understands what a virus is

On the timeline · around May-July 1796 · The Birth of Vaccination and EpidemiologyThe Birth of Vaccination and EpidemiologyEdward Jenner Tests Cowpox Against Smallpox and Creates the First Vaccine1725175017751800182518501875

Quick facts

Innovator
Edward Jenner
Test subject
James Phipps, age 8
Material source
Cowpox sore of milkmaid Sarah Nelmes
Date
Inoculated May 1796; challenged with smallpox July 1796
Term coined
Vaccination, from vacca (Latin for cow)

What happened

By the late 18th century, variolation, deliberately infecting a healthy person with material from a mild smallpox case to induce immunity, was an established but risky practice; between 0.5 and 3 percent of variolated patients still died, and they could spread full-strength smallpox to others while infectious. Edward Jenner, a physician in rural Gloucestershire, had heard rural dairy workers claim that catching cowpox, a much milder disease, protected them from smallpox for life. In May 1796 he tested this directly: he took matter from a cowpox sore on the hand of milkmaid Sarah Nelmes and used it to inoculate an eight-year-old boy, James Phipps, who developed a mild, short illness and recovered fully. Two months later, in July 1796, Jenner deliberately exposed Phipps to material from an active smallpox sore. Phipps did not develop the disease, direct evidence that cowpox exposure had conferred protection.

Why it matters

Jenner named the procedure vaccination, from vacca, the Latin word for cow, and it became the first vaccine in the modern sense: deliberate exposure to a related but far less dangerous pathogen to build immunity against a lethal one. The method spread internationally within years and, nearly two centuries later, became the technical basis for the WHO's successful global smallpox eradication campaign.

How we know

Jenner's own case notes and subsequent publications documented the Phipps experiment and follow-up testing on additional subjects; the World Health Organization's history of vaccination synthesizes this record alongside later verification of the method's effectiveness through expanded trials by 1801.

Sources

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Part of a timelinePandemics Through History24 events · How plague, pox, and pandemic flu remade societies, and how the science of germs and vaccines fought backView all →
Edward Jenner Tests Cowpox Against Smallpox and Creates the First Vaccine · Pandemics Through History · SourcedStory