Measles outbreak in South Africa, 2003-2005

Objectives. Measles was virtually eliminated in South Africa following control activities in 1996/7. However, from July 2003 to November 2005, 1 676 laboratory-con firmed measles cases were reported in South Africa. We investigated the outbreak's cause and the role of HTV. Design. We traced laboratory-confirmed case-patients residing in the Johannesburg metropolitan (JBM) and O R Tambo districts. We interviewed laboratory- or epidemiologically confirmed case-patients or their caregivers to determine vaccination status and, in JBM, HIV status. We calculated vaccine effectiveness using the screening method. Setting. Household survey in JBM and O R Tambo districts. Outcome measures. Vaccine effectiveness, case-fatality rate, and hospitalisations. Results. In JBM, 109 case-patients were investigated. Of the 57 case-patients eligible for immunisation, 27 (47.4%) were vaccinated. Fourteen (12.8%) case-patients were HIV infected, 46 (42.2%) were HIV uninfected, and 49 (45.0%) had unknown HIV status. Among children aged 12 - 59 months, vaccine effectiveness was 85% (95%, confidence interval (CI): 63, 94) for all children, 63% for HIM infected, 75% for HIV uninfected, and 96% for children with unknown HIV status. (Confidence intervals were not calculated for sub-groups owing to small sample size.) In O R Tambo district, 157 case-patients were investigated. Among the 138 case-patients eligible for immunisation, 41 (29.7%) were vaccinated. Vaccine effectiveness was 89%, (95%, CI 77, 95). Conclusions. The outbreak's primary cause was failure to vaccinate enough of the population to prevent endemic measles transmission. Although vaccine effectiveness might have been lower in HIV-infected than in uninfected children, population vaccine effectiveness remained high.