Jenner's smallpox vaccine

English doctor Edward Jenner inoculated a boy with cowpox and later showed he was protected from smallpox. Smallpox was eventually eradicated worldwide in 1980.

Context

Jenner, a country doctor in Gloucestershire, had heard the local belief that people who caught cowpox from cattle did not get smallpox. In May 1796 he took material from a cowpox sore on the hand of a dairymaid, Sarah Nelmes, and inoculated an eight-year-old boy, James Phipps. Weeks later he exposed the boy to smallpox material, and the boy did not develop the disease.

By today's standards the experiment would be considered unethical, and it was small, but Jenner followed it with further cases and published his findings in 1798. The word vaccine comes from the Latin word for cow. Others, including a farmer named Benjamin Jesty, had acted on the same folk idea earlier, but Jenner's systematic study and publication made the method known.

Vaccination spread across Europe and the world during the nineteenth century. After an intensive global campaign led by the World Health Organization, the last natural case occurred in 1977, and the WHO declared smallpox eradicated in 1980. It remains the only human disease to have been eradicated so far.

Smallpox had killed vast numbers of people over centuries, which is why Jenner's method is often counted among the most important medical advances in history.