Estimated prevalence of immunity to poliomyelitis in the city of S o Paulo, Brazil: a population-based survey

OBJECTIVES: Estimate the prevalence of immunity to poliomyelitis (anti-polio antibodies) in the city of S o Paulo/Brazil through a population-based survey. METHODS: A quantitative and inductive method was used to draw a representative sample of the population. Randomization and stratification (based on sex, age and residence region) was done, and 1,059 individuals were studied on a home-visit basis (structured questionnaires and blood samples). A microneutralization test was performed to detect anti-polio antibodies against serotypes 1, 2 and 3. RESULTS: The estimated prevalence of immunity to poliomyelitis was high, with 94.6% prevalence of anti-polio 1 antibodies, 98.8% anti-polio 2 and 91.9% anti-polio 3. Despite this high prevalence, there were significantly lower prevalence levels in some groups, specially among age and residence region groups. DISCUSSION: Routine child immunization and NIDs with OPV have provided excellent levels of serological immunity to poliomyelitis in the population of the city of S o Paulo, Brazil. However, there may be specific groups with a lower prevalence of immunity. Estimations of the prevalence of immunity to poliomyelitis were made in a population-based survey, which could be used as an auxiliary tool for supporting the polio eradication program.