On February 23, 1954, the first mass, school-based trials of Dr. Jonas Salk’s polio vaccine began. The vaccine’s success was first made public in April 1955. By 1959, the Salk vaccine had reached about 90 countries. Less than 25 years after the release of Salk’s vaccine, domestic transmission of polio had been completely eliminated in the United States.

Salk was photographed by Karsh in 1956 and in 1991. See more Karsh portraits of Jonas Salk.