Edward Jenner's earlier experiments with cowpox matter to confer smallpox immunity had already spread by word of mouth, but by January 1799 his findings were being formally disseminated and debated among London's medical establishment. The technique, crude by modern standards, marked the beginning of systematic immunology and eventually led to smallpox's total eradication in 1980.
In 1796, Edward Jenner scraped pus from a cowpox blister on milkmaid Sarah Nelmes's hand and inserted it into two small cuts on the arm of eight-year-old James Phipps. Weeks later, he exposed the boy to smallpox matter directly. Phipps did not fall ill. Jenner had confirmed what dairy folklore had long suspected: contact with cowpox protected against its far deadlier cousin.
By January 1799, Jenner's ideas were circulating through London's medical circles, provoking both fascination and fierce resistance. Critics mocked the notion that infecting people with an animal disease could protect them, and cartoonists drew patients sprouting cow horns. Yet the practical results were undeniable, and vaccination — a word Jenner coined from vacca, the Latin for cow — spread across Europe within a few short years.
Smallpox had killed an estimated 400,000 Europeans annually in the 18th century and disfigured millions more. Jenner's discovery, imperfect and empirically derived rather than theoretically understood, nonetheless launched the field of immunology. Nearly two centuries later, in 1980, the World Health Organization declared smallpox eradicated — the only human disease ever eliminated by vaccination.
Key people: Edward Jenner, James Phipps, Sarah Nelmes