Starting in the 1930's, Poliovirus was a newly-discovered disease that was frightening the world. As with all new diseases, little was known about the transmission or prevention of the disease. It was noted, though, that the disease was mostly affecting children, so it quickly began a research movement to develop a vaccination. The first successful demonstration of a polio vaccine was by Hilary Koprowski in 1950, which used a live virus which people drank. The vaccine was not approved by the United States, but was commonly used successfully elsewhere. The first inactivated polio vaccine was developed by Jonas Salk, and was announced in 1955. This had success in the United States. In 1961, another live oral polio vaccine was commercially released.
