Jonas Salk was an American medical researcher and virologist who developed one of the first successful vaccines for polio. He is widely credited with saving millions of lives and is remembered as one of the most influential scientists of the 20th century. Salk's vaccine, which he developed in 1952, was the first effective vaccine against polio. It was made available to the public in 1955 and quickly became a worldwide success. Salk's work revolutionized the field of immunology and helped to eradicate polio from much of the world.