Edward Jenner created a vaccine for smallpox, a deadly disease that plagued humanity for centuries. In 1796, Jenner conducted experiments using cowpox material, which was milder and related to smallpox. He inoculated a young boy, James Phipps, with cowpox and later exposed him to smallpox; the boy did not develop the disease. This groundbreaking work laid the foundation for immunology and vaccination practices. Smallpox was ultimately declared eradicated in 1980, making it the first disease to be eliminated through vaccination, showcasing the profound impact of Jenner's discovery.