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A program of mass vaccination with oral polio vaccine was launched in 1980 in Brazil. The aim was to reach in a single day, twice a year, the whole population of children younger than five years of age, irrespective of their vaccination history. More than 20 million children were vaccinated in each of the six campaigns carried out until 1982. Recorded rates of immunization exceeded 90% in the target age group. The incidence of poliomyelitis dropped from an average of 2,330 cases in the 1975-1980 period to only 122 cases in 1981. Provisional figures for 1982 indicate that the total number of confirmed cases will be close to 70. Similar campaigns are intended for 1983 and 1984, but the continuation of this strategy after 1984 is still under discussion.
João Baptista Risi (Tue,) studied this question.