Salk, Jonas

Jonas Salk, in full Jonas Edward Salk, (born October 28, 1914, New York, New York, U.S.—died June 23, 1995, La Jolla, California), American physician and medical researcher who developed the first safe and effective vaccine for polio.

Salk received an M.D. in 1939 from New York University College of Medicine, where he worked with Thomas Francis, Jr., who was conducting killed-virus immunology studies. Salk joined Francis in 1942 at the University of Michigan School of Public Health and became part of a group that was working to develop an immunization against influenza.

In 1947 Salk became associate professor of bacteriology and head of the Virus Research Laboratory at the University of Pittsburgh School of Medicine. At Pittsburgh he began research on polio, an acute viral infectious disease of the nervous system that usually begins with general symptoms such as fever and headache and is sometimes followed by a more serious and permanent paralysis of muscles in one or more limbs, the throat, or the chest. In the mid-20th century hundreds of thousands of children were struck by the disease every year. Working with scientists from other universities in a program to classify the various strains of poliovirus, Salk corroborated other studies in identifying three separate strains. He then demonstrated that killed virus of each of the three, although incapable of producing the disease, could induce antibody formation in monkeys.

In 1952 he conducted field tests of his killed-virus vaccine, first on children who had recovered from polio and then on subjects who had not had the disease; both tests were successful in that the children’s antibody levels rose significantly and no subjects contracted polio from the vaccine. His findings were published the following year. In 1954 Francis conducted a mass field trial, and the vaccine, injected by needle, was found to safely reduce the incidence of polio. On April 12, 1955, the vaccine was released for use in the United States. In the following years the incidence of polio in the United States fell from 18 cases per 100,000 people to less than 2 per 100,000. In the 1960s a second type of polio vaccine, known as oral poliovirus vaccine (OPV) or Sabin vaccine—named for its inventor, American physician and microbiologist Albert Sabin—was developed. OPV contains live attenuated (weakened) virus and is given orally.

Salk served successively as professor of bacteriology, preventive medicine, and experimental medicine at Pittsburgh, and in 1963 he became fellow and director of the Institute for Biological Studies in San Diego, California, later called the Salk Institute. Among his many honours was the Presidential Medal of Freedom, awarded in 1977.