American virologist and medical researcher Jonas Salk was born on this day, October 28, in 1914 (d. 1995). In 1947, Salk accepted a professorship in the School of Medicine at the University of Pittsburgh. It was there that he undertook a project to determine the number of different types of poliovirus, starting in 1948. For the next seven years, Salk devoted himself towards developing a vaccine against polio. 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.