Long before vaccines, people protected themselves from smallpox, which killed about 30 percent of those infected, by deliberately catching a mild case. This episode traces variolation from China, where healers as early as the 16th century blew powdered old scabs mixed with musk up the nose through a silver pipe, right nostril for boys and left for girls. Dried scabs carried a lower viral load. In Sudan mothers bargained for infected cloth in a practice called buying the smallpox, and in India tikadars rubbed scabs into needle pricks. Lady Mary Wortley Montagu brought the practice to England, and six condemned prisoners at Newgate survived a 1721 trial in exchange for pardons.

Elite doctors then added deep cuts and bleeding, raising the danger, while the Sutton family’s shallow scratch method treated hundreds of thousands. In Shetland, self taught Johnny Notions variolated about 3,000 people with no recorded deaths. In Boston, Onesimus, an enslaved West African man, told Cotton Mather about the practice, and in 1721 only six of about 300 variolated people died, against 1,000 of 6,000 natural cases.

• A small explosive device thrown through Cotton Mather’s window
• Johnny Notions drying pus with peat smoke and burying it with camphor for up to eight years
• George Washington ordering variolation of the Continental Army in 1775
• Catherine the Great’s relay of horses for Thomas Dimsdale’s escape in 1769
• Edward Jenner’s cowpox vaccine, Russia’s 1805 ban, and pox parties