In 1796 Jenner found a milkmaid with cowpox and injected the matter from one of her sores into an eight-year-old boy, who developed a mild fever and a loss of appetite but recovered quite quickly. Ten days later, Jenner proceeded to inject the boy with actual smallpox. The boy survived! With no signs of smallpox. That experiment sounds terrifying, but it worked. Jenner called the technique vaccination, as vacca was the Latin word for “cow.”
This must be one of medicine's greatest discoveries, I mean who would've thunk??
