1956: Dr. Albert Sabin announces that his live-virus oral polio vaccine is ready for mass testing. It will soon supplant the Salk vaccine.

Poliomyelitis is an infectious disease caused by viruses. Its effects range from complete recovery to death. Intermediate possibilities are mild after-effects, moderate to severe paralysis of a limb or limbs, or paralyzed chest muscles, necessitating the confining but lifesaving use of an iron lung.

Polio epidemics periodically ravaged American cities in the first half of the 20th century. Children were especially vulnerable, but the disease also struck...