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The epidemiology of measles in a partially vaccinated population in an African city: implications for immunization
1International Health Program Office, Centers for Disease Control, Atlanta, GA 30333.
Abstract:
A large outbreak of measles was reported in Pointe-Noire, Congo, between October 1984 and March 1985. An investigation was conducted to determine the epidemiology of measles in this community in which, in 1985, 54% of the children 12-23 months of age had documented evidence of vaccination against measles. The investigation included hospital and clinic record reviews and a community survey. Measles has been continuously transmitted in Pointe-Noire since at least 1979, with seasonal epidemics. In early 1984, the expected epidemic did not occur, and at least 1,000 measles hospital admissions and 100 measles deaths were prevented. Between October 1984 and March 1985, 1,942 measles cases were hospitalized, of which 306 (15.8%) died. During the epidemic, the proportion of nonpreventable cases (cases occurring before nine months of age) was 17%, reflecting the change in age distribution of measles cases in childhood since the immunization program started in Pointe-Noire in 1982. From the community survey, it was estimated that 13% of all children under age five years acquired measles in Pointe-Noire in 1985. Vaccine efficacy was calculated from community and hospital samples to be between 78% and 87%. Our findings suggest that increasing vaccination coverage levels to well above 50% is necessary to substantially reduce measles morbidity and mortality in African cities.
Insights
A large measles outbreak in Congo highlights the need for higher vaccination coverage. Increasing immunization rates above 50% is crucial to significantly reduce measles cases and deaths in African urban areas.
Area of Science:
- Epidemiology
- Public Health
- Vaccinology
Background:
- Measles outbreaks pose a significant public health threat in African cities.
- Pointe-Noire, Congo, experienced a measles epidemic from October 1984 to March 1985.
- Routine measles vaccination began in Pointe-Noire in 1982, with 54% coverage in 12-23 month olds in 1985.
Purpose of the Study:
- To investigate the epidemiology of measles during a large outbreak in Pointe-Noire.
- To determine the impact of the measles outbreak on morbidity and mortality.
- To assess measles vaccine efficacy in the studied population.
Main Methods:
- Hospital and clinic record reviews.
- Community-based survey.
- Epidemiological analysis of measles cases and deaths.
Main Results:
- 1,942 measles cases were hospitalized, with a 15.8% mortality rate.
- 13% of children under five acquired measles in 1985.
- Measles vaccine efficacy was estimated between 78% and 87%.
Conclusions:
- Measles transmission has been continuous in Pointe-Noire since 1979.
- Increased vaccination coverage above 50% is essential to reduce measles morbidity and mortality in African urban settings.
- Changes in measles case age distribution were observed post-immunization program initiation.