Immunity levels to poliomyelitis in a sample of school children from the city of S. Paulo, Brazil

Abstract

The prevalence of neutralizing antibodies for the three types of polioviruses and the immunity levels of different age groups were determined through a sero-epidemiological survey, in the elementary school children population from the São Paulo public school system. The investigation was based on a representative sample of the school population - a total of 1.486 children was studied - and the immunity levels were determined in 13 Public Administrative Regions, as well as in the three geographical zones of S. Paulo city. The results showed that only about a half of the children had antibodies to all three poliovirus types in the different age groups examined, except in the 13 year age bracket, where the percentage of triple-immunes was 68.0%. Consequently, the immune status of the population does not reach the desirable levels of 75% of triple positives and the principal cause for this situation was the relative low prevalence of antibodies to the type 3 poliovirus, in almost all the age groups studied. It was also shown that the immune status of the school population was similar in the three geographical zones of the city. However, significant differences in immunity were detected in the 13 Public Administrative Regions of S. Paulo city, where the percentages of triple positive children varied from 38.6% to 66.9%. Booster doses of oral vaccine were recommended for children at school age.