The first vaccine was tested on an 8-year-old using pus from a milkmaid's cowpox sore

In 1796 Edward Jenner scraped matter from a cowpox blister on milkmaid Sarah Nelmes and inoculated young James Phipps with it, then deliberately exposed him to smallpox. Phipps stayed healthy, and Jenner's technique became the world's first vaccine, a word rooted in the Latin for cow.

— Michael Bennett, War Against Smallpox: Edward Jenner and the Global Spread of Vaccination — Cambridge University Press, 2020
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