[Observation on the epidemiologic efficacy for 9 years on epidemic meningococcal polysaccharide vaccine of group A by district immunization method].

According to previous studies, there might be a peak of epidemic meningitis in Baoding City in 1984. For preventing the epidemic, we carried out vaccination with meningococcal polysaccharide vaccine by district immunization method during the 1980-1984 and then vaccination only to the children aged 12-24 months every year. The vaccination rate was 80.01% in 1980-1984 and was 97.15% in 1985-1988. During the 9 years, 833,377 children of vaccination group were observed, 4 of whom developed this disease, with an incidence of 0.48/100,000; and 304,085 children in the control group were observed, 25 of whom contracted this illness, with an incidence of 8.22/100,000. The protective rate of vaccine was 94.16% and the efficacy index was 1:17.12. This result showed that peak year of epidemic meningitis predicted in 1984 was prevented by vaccine immunization and the incidence of this disease was continuously kept less than 1/100,000 for 9 years.