It began, as many things do, with a need, a curiosity, and an intriguing story. In the 18th century, smallpox was a global scourge. About a third of those who caught the disease died; survivors were left scarred, sometimes disfigured. From uncertain origins, smallpox had spread across the world through human movement – for trade, conquest and exploration. Early control methods such as variolation – scratching pus from smallpox sores into the skin of a disease-free person (named after the virus, Variola) – were only mildly successful.
In 1796, English physician Edward Jenner noted the accepted wisdom that milkmaids who’d caught cowpox – a similar but harmless cousin of smallpox – were more protected from the deadlier virus. Jenner guessed that cowpox might offer protection and, to test his theory, took pus from a cowpox sore on the hand of milkmaid Sarah Nelmes, who’d caught the infection from a milker named Blossom. Then, he injected it into both arms of James Phipps, the nine-year-old son of his gardener. Months later, Jenner directly exposed Phipps several times to variola virus, but Phipps never developed smallpox. After successfully testing his methodology on 23 more people, Jenner published On the Origin of in 1801.
