The Smallpox Vaccine (1796)

Edward Jenner's development of the smallpox vaccine in 1796 — the first vaccine ever created — not only saved tens of millions from a disease that killed 300 million people in the 20th century alone but established the entire concept of vaccination that has since eradicated smallpox (1980) and controlled polio, measles, typhoid, yellow fever, and dozens of other historically devastating diseases. The WHO estimates vaccines prevent 3 to 4 million deaths annually.