Poliomyelitis in Japan during the period 1962-68 after the introduction of mass vaccination with Sabin vaccine.

After the mass vaccination of children of susceptible age groups in Japan in 1961, the incidence of poliomyelitis decreased markedly. From 1962 to 1968 a total of 659 paralytic cases were officially notified. Detailed investigations of 626 cases reported to the Poliomyelitis Surveillance Committee revealed that only 185 (29.6%) were cases of paralysis clinically typical of poliomyelitis. Tests on 120 of these 185 cases showed that 75 (62.5%) were positive for poliovirus: 45 of these positive cases were temporally associated with the administration of live poliovirus vaccine and 36 had some residual disability. Wild types of poliovirus were rarely isolated. Only 36 vaccine-related cases of poliomyelitis were observed among the total of more than 11 million newborn infants vaccinated with Sabin vaccine in the period 1962-68.