Sharon Cunningham, age 14, of Danville, I11., for her question:

WHEN WAS SALK VACCINE DEVELOPED?

Salk's vaccine was the first vaccine developed that greatly reduced the disease of poliomyelitis. It was developed by an American physician and epidemiologist named Jonas Salk.

Salk's work in the 1940s on an anti influenza vaccine led him and his colleagues to develop an inactivated vaccine against polio in 1952. After successful wide scale testing in 1954, the vaccine was distributed nationally and greatly reduced the disease.

In the mid 1950s the American virologist Albert Sabin developed an oral, attenuated (live) vaccine, which with Salk's discovery brought polio under control.

In 1963 Salk became the director of the Salk Institute for Biological Studies in San Diego, Calif. Born in New York City, he had received an M.D. from New York University in 1939 and was appointed assistant professor of epidemiology at the University of Michigan. In 1947 he became head of the virus research laboratory at the University of Pittsburgh and was later research professor of bacteriology (1949 54), professor of preventive medicine and chairman of the department (1954 56) and professor of experimental medicine (1957 63).