On April 12, 1955, the Salk vaccine was announced to be “safe, effective, and potent,” setting off a chain of events that would lead to the virtual elimination of polio from the United States and much of the developed world.

Jonas Salk, the lead scientist in the development of the vaccine, was born in New York City on October 28, 1914. His parents were Russian-Jewish immigrants who, although they themselves lacked formal education, were determined to see their children succeed, and encouraged them to study hard. Jonas was the first member of his family to go to college. He entered the City College of New York intending to study law, but soon became intrigued by medical science.

In 1947, Salk accepted an appointment at the University of Pittsburgh Medical School. While working there, with the National Foundation for Infantile Paralysis, Salk saw an opportunity to develop a vaccine against polio, and devoted himself to this work for the next eight years.

Polio, or poliomyelitis, is an infectious viral disease that attacks nerve cells and the central nervous system, causing muscle wasting, paralysis and even death. Before 1950, the disease affected tens of thousands of victims, perhaps the most famous of which was Franklin Delano Roosevelt, the 32^nd president of the United States.

Salk's vaccine is an example of an inactivated vaccine. It is made by growing virulent polio virus in tissue culture, then treating the virus with formaldehyde so that it cannot reproduce in the person who receives the vaccine. Salk’s polio vaccine was so groundbreaking that within one month of its public release 4,000,000 doses had been administered, and 450,000,000 had been administered within its first four years. Several years after its discovery, the Salk vaccine was replaced by the Sabin vaccine. The Sabin vaccine is more effective as it is made from a live but weakened polio virus, and it gained widespread use because it could be administered orally, while Salk's vaccine required injection. The success of these polio vaccines has been so great that there has not been a new case of polio in the United States since 1975 and across the Western Hemisphere since 1991.

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