In 1796, Gloucestershire physician Dr Edward Jenner conducted one of the most important, if unethical, experiments in medical history. His aim was to investigate claims that people could be protected from deadly smallpox if previously exposed to cowpox, an apparently related but harmless disease. To find out, he risked the life of an eight-year-old boy (whom he had exposed to cowpox) by deliberately exposing him to smallpox. Apart from a brief fever following the cowpox infection, the boy remained healthy. Ever since, Jenner has been hailed as the discoverer of ‘vaccination’, a vital weapon in the fight against disease and one that led to the global elimination of smallpox in 1980.
The idea that prior infection gave ‘immunity’ against later disease had, however, been noted as early as the 10th Century by Chinese physicians. By the early 18th Century, Lady Mary Wortley Montagu, wife of a diplomat in Turkey, was advocating ‘variolation’. This involved deliberately exposing patients to smallpox-infected tissue. While often successful, the technique was risky, with around one in eight dying from smallpox.
Jenner was not even the first person to test cowpox as a way to provide immunity against smallpox. Even so, he deserves credit for studying the theory systematically, and convincing the Royal Society to publish his findings.