The seroepidemiology of poliovirus in yaoundé, cameroon, 1977: A survey following one year of immunization

Neutralizing antibodies against poliovirus were studied in 358 children, in Yaoundé, Cameroon. Among children without a history of immunization, the prevalence of antibodies to each poliovirus type rose from about one-third of children under 1 year of age to nearly 90% of those 4-5 years of age. In children under 1 year of age immunized primarily with live attenuated trivalent oral polio vaccine (T.O.P.V.) the prevalence of antibodies was about 80%. It appeared that unimmunized children under 2 years of age had a higher prevalence of antibodies than was determined for this age group in a 1971 serosurvey. In the 14 months prior to this 1977 serosurvey, a community-wide multiple antigen immunization programme had given 15,500 doses of T.O.P.V., reaching more than 20% of the under 1 year old and nearly 30% of the under 3 year old populations. The data suggest that the epidemiology of poliovirus has changed and that the spread of attenuated vaccine virus from immunized children to their unimmunized contacts may have been occurring even at this low level of coverage.