Salk first announced his polio vaccine on the radio in 1953

Jonas Salk first announced his polio vaccine on 26 March 1953, telling a CBS national radio audience that he had successfully tested a vaccine against the virus that causes polio. His results appeared in the Journal of the American Medical Association two days later, and it would be another two years before the vaccine was proven to work.

The broadcast came in the middle of an epidemic era. In 1952 the United States recorded about 58,000 new polio cases and more than 3,000 deaths. Salk’s vaccine, later known as inactivated poliovirus vaccine (IPV), contained killed virus and was given by injection.

Many retellings say Salk tried the vaccine on himself and his family before going on air. The dates do not fit. The History of Vaccines timeline, published by the College of Physicians of Philadelphia, records him injecting himself, his wife and their three sons on 16 May 1953, seven weeks after the broadcast. The early human tests behind the March announcement included children who had already had polio.

The radio address was a promise rather than proof. What makes it notable is how quickly the promise was kept:

• April 1954: a field trial involving nearly two million schoolchildren begins.
• 12 April 1955: at the University of Michigan, researchers announce the vaccine is 80–90% effective against paralytic polio; the US government licenses it the same day.
• 1953 to 1957: after a national vaccination drive, annual US cases fall from 35,000 to 5,600.
• 1961: only 161 cases are recorded in the United States, where the disease has since been wiped out.

Within eight years of Salk’s broadcast, a disease that had filled hospital wards each summer had become rare in the country that heard it.