Poliomyelitis control in Japan

The Sabin oral poliovirus vaccine ( OPV ) has been used in Japan since 1961. Since then the number of paralytic cases has decreased markedly. The incidence of paralytic and positive rates for antibodies to poliovirus were analyzed. The number of paralytic cases associated with OPV was low for cases due to type 1 virus and high for those due to type 2 virus. As for cases due to type 3 virus, the number was high until 1969 and has been low since 1970. This difference was brought about by changing the batch of type 3 virus used in the preparation of OPV . The analysis of titers of neutralizing antibody showed that response to type 1 virus in OPV used in 1977 and to type 3 virus in OPV used in 1972 and 1973 was not adequate. Both situations were improved by changing the batches of virus used for OPV . These experiences suggest that the use of good batches is necessary for safety and efficacy of OPV .