Immunization during a cerebrospinal meningitis epidemic in the Mongolian People's Republic, 1974-75.

An epidemic of cerebrospinal meningitis (CSM) in the Mongolian People's Republic, starting in 1969, reached its peak in 1974. In that year and in early 1975, 65 000 children in the 0-8-years age group in the main towns and in the provinces were immunized with meningococcal vaccine of serogroup A. The morbidity rates due to CSM were 12 times higher in the non-immunized than in the immunized children.