It was a red-letter day in the history of medicine – ‘Target Zero Day’, 8 May 1980, signified the complete eradication of smallpox, a terrifying scourge that had previously killed one in 12 worldwide. Smallpox was untreatable but, luckily, it turned out that vaccination provided good protection – and that intensive immunisation could exterminate the smallpox virus by blocking its spread.
According to legend, vaccination was invented by Dr Edward Jenner of Berkeley, Gloucestershire. Jenner showed that healthy children inoculated with cowpox, a mild infection of cattle, could not catch smallpox. He was supposedly inspired by a comment from a local milkmaid, but there is evidence the idea came from a medical friend, John Fewster, who had experimented with cowpox. Vaccination goes back even further. In 1774, a Dorset farmer,…