Vaccination status and seroprevalence of measles and polio antibodies in 1-6-year-old children in the Elim health ward of Gazankulu.

Seroprevalence was used to evaluate the vaccination programme in the Elim health ward of Gazankulu. Antibodies to measles and polio were measured in 1-6-year-old children together with vaccination status. In 224 children studied using a cluster sampling technique, vaccine coverage was found to be 86% for measles and over 90% for polio and diphtheria, pertussis and tetanus. It was difficult to determine vaccine failure rates accurately; 21% of children were seronegative after having received measles vaccine, 32% who had apparently not been vaccinated had antibodies, while a total of 27% had no measles antibodies. Thirty-nine per cent of children failed to demonstrate antibodies to all 3 types of poliovirus after having received 3 doses of oral polio vaccine, 94% had immunity against type 2, and 76% and 74% were immune to types 1 and 3, respectively. Reasons for diminished effectiveness of vaccination programmes are cited; in this study it was probably due to decreased vaccine efficacy related to inadequacies in the cold-chain. Recommendations are that seroprevalence studies are useful, but only after vaccine coverage and the cold-chain have been optimised.