What was the first vaccine ever developed?

The smallpox vaccine was the first vaccine ever developed. In 1796, English physician Edward Jenner showed that exposure to cowpox could protect people from the much deadlier smallpox virus.

Jenner’s work grew from an observation that milkmaids who had caught cowpox often seemed protected from smallpox. He tested the idea by inoculating a boy, James Phipps, with material from a cowpox sore and later demonstrating that the boy resisted smallpox infection. Jenner published his findings in 1798.

The word vaccine comes from vaccinia, the name associated with the cowpox-related virus used in smallpox vaccination. Early vaccination methods were very different from modern injections, often using material transferred from pustules or preserved on threads. Over time, safer and more standardized preparations were developed.

Smallpox vaccination became a foundation of immunology and one of the great public-health successes. A coordinated global campaign led by the World Health Organization eliminated naturally occurring smallpox, with the last known natural case reported in 1977.