Jonas Salk's inactivated polio vaccine (IPV) was developed in the early 1950s, tested in 1954, and licensed on April 12, 1955, leading to a significant drop in annual U.S. polio cases from 58,000 to 5,600 by 1957. The subsequent Global Polio Eradication Initiative, launched in 1988, has reduced polio cases by over 99%.