Jonas Salk developed the first widely successful polio vaccine, whose success was announced in 1955. An American virologist and medical researcher, Salk led the work at the University of Pittsburgh during a period when polio regularly paralyzed or killed children.
Salk chose an inactivated vaccine, using polioviruses that had been killed chemically rather than weakened live viruses. This approach was controversial because some researchers favored live-virus vaccines, but it offered a way to train the immune system without causing infection. Early testing included children in Pittsburgh, followed by the enormous Francis Field Trial led by Salk's mentor, Thomas Francis Jr.
The trial involved about 1.8 million children across the United States. On April 12, 1955, Francis announced that the vaccine was safe, effective, and potent. The news triggered celebrations and rapid vaccination campaigns. Salk did not patent the vaccine, believing broad distribution mattered more than personal profit.
Albert Sabin later developed a different oral polio vaccine using weakened live virus. Sabin's vaccine became important worldwide, but it was not the vaccine announced as successful in 1955.