Today the deadly and debilitating poliomyelitis virus is only endemic in four countries—Afghanistan, India, Nigeria, and Pakistan. This is- thanks to the groundbreaking research undertaken by U.S. medic and biologist Jonas Salk (1914-1995).
In 1947, at the University of Pittsburgh, SaIk combined his work on the influenza vaccine with searching for a vaccine to protect against polio. The virus was deadly in 5 to 10 percent of cases where patients became paralyzed, and thus were unable to breathe. Medical opinion at the time held that only a live virus could prompt complete immunity, but Salk disproved this. In 1952 he used formaldehyde to inactivate the polio virus and developed a vaccine still capable of triggering an immune response in a host. Initially tested on monkeys, then patients at the D. T. Watson Home for Crippled Children, Salk's success convinced him to test it on himself, his family, his staff, and other volunteers.
In 1954 one of the earliest double-blind, placebo- controlled trials ever gave the vaccine to one million children aged between six and nine years, and a placebo to another million of the same age. A year later, the children treated with vaccine had developed immunity to the live disease. In 1952 there were 57,628 cases of polio recorded in the United States. Following vaccine use, this fell 85 to 90 percent in two years.
An oral vaccine replaced Salk's injectable version in 1961 after Albert Sabin developed a live dose administered on a sugar lump. More recently, the United States and United Kingdom have reverted to Salk-type injectables of the inactivated virus.
