In 1796, English doctor Edward Jenner gambled his career on an experiment.
He exposed James Phipps, an eight-year-old boy, to a mild disease called cowpox. Then, about six weeks later, he infected the same boy with a deadly, highly contagious disease called smallpox. Jenner believed that people like James who caught cowpox were protected against smallpox. He was proved right, and within five years people all over the world were using Jenner’s smallpox vaccination. Suddenly, a disease that killed millions began dying out. In 1980, smallpox became extinct.
Today, Americans on average live almost twice as long as they did in Jenner’s time. The credit for that goes largely to a surge in medical and scientific knowledge that, while not caused by the Industrial Revolution, happened at about the same time.