Eradication of poliomyelitis in the United States. I. Live virus vaccine-associated and wild poliovirus disease.

The patterns of incidence of poliovirus disease in the United States are analyzed. A category of live poliovirus vaccine-associated paralysis is defined that includes those cases associated with vaccine virus but with no known history of exposure to the vaccine (indirect community contact). Domestically arising wild poliovirus disease has essentially been eradicated from the United States, whereas the incidence of vaccine-associated disease has been constant at approximately nine cases per year. The age distribution of vaccine-associated disease reflects patterns ofuse of the vaccine rather than intrinsic differences in susceptibility believed to be associated with age. Eighty-eight percent of vaccine-associated cases of poliomyelitis occur in individuals with a normal immune system.