[Changes in the age distribution of meningococcal diseases in Czechoslovakia].

Based on an analysis of the specific morbidity by age, we tried to explain the development of the morbidity from meningococcal meningitis in the CRS during the past 35 years. After the epidemic of meningococcal meningitis at the beginning of the fifties, the morbidity had a declining trend to the mid-seventies. During the period between 1975 and 1984 there was a rising trend of the notified morbidity, while in the subsequent years a decline followed. From the analysis of the specific morbidity by age it is obvious that during the period between 1972-1986 a significant rise of the morbidity of the age groups 0-11 months, 15-19 years and 25-29 years occurred. Analysis of the morbidity of five-year cohorts of subjects born in 1947-1971 revealed that after 1977 ex post herd immunization of all cohorts occurred with the exception of the cohort born in 1947-1951 which acquired a maximum immunity state already in the epidemic at the beginning of the fifties. The authors express the hypothesis that these changes are directly associated with the antigenic changes of N. meningitidis.