Measles mortality and vaccine efficacy in rural West Africa.

Measles mortality and measles vaccine efficacy were determined during outbreaks in three Gambian villages. There were 146 cases of measles among 1073 children younger than 11 years. 30% of the children had been vaccinated against measles. The attack rate in unvaccinated children aged 9-47 months was 43% compared with 6% for children of the same age with documented measles vaccination. Vaccine efficacy was 37% for children vaccinated at 6-8 months of age and 89% for children vaccinated at 9 months or older. 5% of measles cases died before the initial investigation of the outbreaks and a further 10% of cases died during the ensuing 9 months. Only 1% of children who did not contract measles died in the 9 months after the outbreaks. Case-fatality rates were highest for measles patients less than 1 year old (64%) and fell with age. Measles remains a significant source of acute and delayed mortality in unvaccinated African populations.