Polio vaccine The results of the field trial were announced 12 April 1955 (the tenth anniversary of the death of President Franklin D. Roosevelt, whose paralytic illness was generally believed to have been caused by polio). The Salk vaccine had been 60–70% effective against PV1 (poliovirus type 1), over 90% effective against PV2 and PV3, and 94% effective against the development of bulbar polio. Soon after Salk's vaccine was licensed in 1955, children's vaccination campaigns were launched. In the U.S, following a mass immunization campaign promoted by the March of Dimes, the annual number of polio cases fell from 35,000 in 1953
Jonas Salk got in. During his years at New York University Medical School, Salk worked as a laboratory technician during the school year and as a camp counselor in the summer. During Salk's medical studies, he stood out from his peers, according to Bookchin, "not just because of his continued academic prowess—he was Alpha Omega Alpha, the Phi Beta Kappa Society of medical education—but because he had decided he did not want to practice medicine." Instead, he became absorbed in research, even taking a year off to study biochemistry. He later focused more of his studies on bacteriology which had replaced medicine