CHANGING EPIDEMIOLOGY OF MEASLES IN AFRICA

Tuesday, 4th of February 2014

[source]Journal of Infectious Diseases[|source]

In 2009, WHO African member states endorsed a goal of >98% reduction in measles mortality by 2012, compared with mortality in 2000, and an additional goal of regional measles elimination by 2020 was adopted. The changed and indeed higher goals were building on the experiences of accelerated measles control efforts that had started as early as 1999. The strategy to attain measles control/elimination remaining largely: (a) increasing routine vaccination coverage with the first dose of measles-containing vaccine (MCV1) for all children, (b) providing a second dose of MCV to be given through supplemental immunization activities (SIAs), (c) improving measles case management, and (d) establishing case-based surveillance with laboratory confirmation for all suspected measles cases.

Over the years, many reports have documented thee implementation status and achievements of implementing this strategy on the continent. However, few reports had used the massive case-based measles surveillance data to describe the changing epidemiology of measles in Africa. In this report, the authors analyze case-based measles surveillance data to describe current measles epidemiology in Africa and explored the relationship between increasing MCV coverage and the age distribution of cases. A shifting age-distribution of measles is documented as measles coverage increased. More details are available at:  http://jid.oxfordjournals.org/content/204/suppl_1/S205.long

 

Abstract

Background: In Africa before the introduction of measles vaccination, measles primarily affected young children. To describe measles epidemiology in Africa since the start of accelerated measles control activities in 2001, we analyzed regional measles case-based surveillance data for 2002–2009.

Methods: Country-years were grouped by 10-year moving average of routine measles vaccination coverage (aMCV1). Age was log transformed, and pair-wise comparisons of means were made. A χ² test was used to assess association between coverage and age groups. Cumulative percent curves and percentiles of age, dot plots with Loess curve, and Spearman rank correlation coefficient were calculated.

Results: Of 180,284 suspected cases, 73,009 (41%) were confirmed as measles. Of these, the mean age was 79 months (median, 36 months; interquartile range, 16–96 months) and significantly younger in country-years with <50% aMCV1 than those with 50%–74% aMCV1 (P = .03) and ≥75% (P = .02). With increasing coverage, there was a slight decrease in age in the 10th and 25th and moderate increase in age in the 50th, 75th, and 90th percentiles.

Conclusions: During 2002–2009, the median age of confirmed measles was 36 months. In countries with ≥50% aMCV1 coverage compared with low-coverage countries, age shifted to older children and young adults; for infants, age decreased slightly with higher coverage.