The first vaccine against polio, developed by Jonas Salk in 1954 while he was at the University of Pittsburgh School of Medicine, registered a success rate of only 60 to 90 percent. Yet the annual incidence of polio in the U.S. quickly and dramatically fell from tens of thousands of cases to a few dozen in only a few years.
The initial Salk vaccine, a “killed-virus” version, was replaced within a few years by a “live-virus” formulation developed by Albert Sabin of the University of Cincinnati. Since 2000, however, an updated version of the Salk vaccine, safer than the Sabin version, has been the only one given in the U.S. to prevent polio: it is 99 percent effective after three doses. Salk never patented nor made any money from his discovery.
In later life Salk went on to found the Salk Institute for Biological Studies in La Jolla, Calif., and in the mid-1980s he started working on an AIDS vaccine. He died in 1995 at the age of 80
Polio: Pushed to the Brink—Scientific American Classics digital issue
“Vaccines For Poliomyelitis,” by Jonas Salk. Scientific American, April 1955 (included in e-book above)