An almost fatal bout of lobar pneumonia when he was a child led to his becoming a medical researcher and an important member of the team that developed the Salk vaccine for polio in 1955. Before that, an average of 50,000 children in the US were struck by polio every year. Within six years of the team's developing the vaccine and making it available to the public, vaccinations had reduced the numbers of polio cases reported each year to fewer than 1,000, and by 1979 the disease had been, for all practical purposes, eliminated.