| English surgeon Edward Jenner, born this day in 1749, discovered the smallpox vaccine. Smallpox was the leading cause of death in the 18th century, which was magnified by occasional outbreaks of special intensity. Jenner noticed that those afflicted with cowpox—a relatively harmless disease that could be contracted from cattle—were not affected by smallpox. In 1796 Jenner successfully used the cowpox virus to create a smallpox vaccine. |