SEROPREVALENCE OF ANTIBODY AGAINST POLIOVIRUS IN INNER-CITY PRESCHOOL-CHILDREN - IMPLICATIONS FOR VACCINATION POLICY IN THE UNITED-STATES

Objectives.-To assess susceptibility to poliomyelitis in selected inne r-city preschool children in the United States and to estimate the con tribution of secondary spread of live attenuated oral poliovirus vacci ne virus to type-specific immunity, Design.-Cross-sectional seropreval ence study, Methods.-Serum neutralizing antibody levels against poliov irus types 1, 2, and 3 were analyzed according to vaccination status, agp, and other sociodemographic variables, Setting.-Hospital and satel lite clinics serving inner-city populations in Houston, Tex, and Detro it, Mich, 1990 to 1991, Participants.-A total of 526 children aged 12 to 47 months seeking medical care were enrolled in the seroprevalence study; 144 children aged 12 to 35 months without a history of previous oral poliovirus vaccination were enrolled in the secondary spread stu dy. Results.-Seropositive rates were similar in children in both citie s, ranging from about 80% for types 1 and 3 in 12- to 23-month-old chi ldren to more than 90% in those aged 36 to 47 months. The most importa nt predictor of seropositivity was the number of doses of oral poliovi rus vaccine received (P<.01), with levels approximately 90% for all 3 serotypes among children who had received 3 or more doses. In children likely to have been unvaccinated, seropositive rates ranged from 9% t o 18% for poliovirus types 1 and 3 and from 29% to 42% for type 2; sec ondary spread of vaccine virus appeared to have occurred among childre n who had previously received 1 dose or less but not those with 2 or m ore doses. Conclusions.-Levels of immunity to poliovirus among inner-c ity preschoolers are high and may be predicted by the number of doses of oral poliovirus vaccine received, Secondary spread of the vaccine v irus plays a modest role in increasing polio immunity in inner-city po pulations, especially against types 1 and 3, This role will decrease i n importance if the recently attained high levels of immunization cove rage in the United States are sustained and if the risk of importation of wild poliovirus continues to diminish.