For persons who were alive during the height of the polio epidemics, the introduction in 1955 of the Salk vaccine, an intramuscular preparation containing killed poliovirus, was nothing short of a medical miracle.

The Salk vaccine was followed in 1961 by the Sabin oral vaccine, which contained live poliovirus that had been attenuated, or weakened. By the mid-1960s, with massive immunization campaigns underway, the incidence of new polio cases had dropped to about 0.01 per 100,000 persons per year.

The Sabin vaccine itself very rarely causes paralytic polio -- an estimated 1 case per 9.5 million doses in vaccine recipients, as well as 1 case for every 3.2 million doses in inadequately vaccinated caretakers and contacts of vaccine recipients. On a global basis, vaccination efforts by the WHO -- part of an ongoing plan to eradicate the virus by the year 2000 -- have been extremely successful, dramatically reducing the number of cases worldwide from hundreds of thousands of new cases per year to just a few thousand cases per year.

RETURN