Immunization Science

Measles Control in Africa

The article

Public-health impact of accelerated measles control in the WHO African Region 2000-03. M Otten, R Kezaala, A Fall, B Masresha, R Martin, L Cairns, R Eggers, R Biellik, M Grabowsky, P Strebel et al. The Lancet, 2005;366(9488):832-839.

Explanatory note: In 2000, sub-Saharan Africa had 58% of worldwide measles deaths. The World Health Organization (WHO) and other organizations have implemented measles-elimination initiatives in several African countries. WHO’s strategy for eliminating measles includes four components: improved routine immunization, a second opportunity for measles vaccination during supplemental immunization activities (SIA), measles case management, and measles surveillance. Nineteen African countries, seven in southern Africa and twelve in western and eastern Africa, undertook measles SIA between 2000 and June, 2003.

The question

What has been the effect of the measles control activities implemented by the World Health Organization in Africa on the numbers of measles cases and deaths?

The study

The researchers used three sources of epidemiological data to assess the effect of accelerated control efforts on the burden of measles: aggregate routine surveillance data, case-based surveillance data, and information from outbreak investigations.

From the aggregate routine surveillance data, the researchers compared the average annual number of reported measles cases in the 6 years before the start of SIA with the average annual number of reported measles cases after the SIA.

Case-based surveillance data, in which material from suspected clinical cases was further assessed by reference laboratories, was used to assign each country to one of three categories of measles transmission: very low; low intermittent; or moderate continuing.

Outbreak investigations were conducted to determine the source and scope of spread, also using a reference laboratory to aid in the investigation.

The researchers estimated that measles deaths was proportional to the number of cases of measles. Measles vaccination coverage in the region was based on reports made to WHO.

The findings

This study found that the average decline in measles cases for countries in the region was 91%. Both measles virus transmission and measles deaths were notably reduced in 17 of the 19 countries that implemented SIA.

The researchers estimated that for the African Region as a whole, annual measles deaths decreased by 20% due to the control activities implemented in 19 countries.

The relevance/bottom line

Region-wide measles immunization strategies can lower measles cases and deaths in regions where the disease remains active.

NNii’s comment

The Public Health workers faced many obstacles in collecting and analyzing their data. Programs differed across the study countries; there were isolated areas where vaccine acceptance was low; and measles spread from neighboring countries without similar programs. The researchers had to use differing methods to measure cases and deaths. The estimates of baseline measles disease burden was based on historical, and at times imputed, figures.

Despite study design limitations, the study implies that these public health measures were cost effective in reducing measles cases and deaths.