MEASLES OUTBREAK IN SOUTH AFRICA: EPIDEMIOLOGY OF LABORATORY-CONFIRMED MEASLES CASES AND ASSESSMENT OF INTERVENTION, 2009–2011

Tuesday, 14th of January 2014

[source]PLoS One[|source]

In the World Health Organisation (WHO) African region, routine measles vaccination is offered at nine months of age but about 15% of children vaccinated at this age will not develop protective immune response. In addition, not all children will receive measles vaccine. As a result the number of susceptible individuals may accumulate over time with the potential for outbreaks to occur. To prevent outbreaks, a second opportunity for measles vaccination is offered through routine services or supplemental immunization activities (SIAs). However, to eliminate measles, coverage for both routine schedule and SIAs must be maintained at >95% throughout the country.

In this article, the authors analyzed the epidemiological characteristics of the 2009 to 2011 measles outbreak in South Africa and discuss the findings in relation to the measles control practices in the country and region in general. In addition, they evaluated the effectiveness of the 2010 nationwide periodic supplementary measles vaccination campaign in seven of the nine provinces in South Africa. More technical details are available at:  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3577838/

Abstract

Background: Since 1995, measles vaccination at nine and 18 months has been routine in South Africa; however, coverage seldom reached >95%. We describe the epidemiology of laboratory-confirmed measles case-patients and assess the impact of the nationwide mass vaccination campaign during the 2009 to 2011 measles outbreak in South Africa.

Methods: Serum specimens collected from patients with suspected-measles were tested for measles-specific IgM antibodies using an enzyme-linked immunosorbent assay and genotypes of a subset were determined. To estimate the impact of the nationwide mass vaccination campaign, we compared incidence in the seven months pre- (1 September 2009–11 April 2010) and seven months post-vaccination campaign (24 May 2010–31 December 2010) periods in seven provinces of South Africa.

Results: A total of 18,431 laboratory-confirmed measles case-patients were reported from all nine provinces of South Africa (cumulative incidence 37 per 100,000 population). The highest cumulative incidence per 100,000 population was in children aged <1 year (603), distributed as follows: <6 months (302/100,000), 6 to 8 months (1083/100,000) and 9 to 11 months (724/100,000). Forty eight percent of case-patients were ≥5 years (cumulative incidence 54/100,000). Cumulative incidence decreased with increasing age to 2/100,000 in persons ≥40 years. A single strain of measles virus (genotype B3) circulated throughout the outbreak. Prior to the vaccination campaign, cumulative incidence in the targeted vs. non-targeted age group was 5.9-fold higher, decreasing to 1.7 fold following the campaign (P<0.001) and an estimated 1,380 laboratory-confirmed measles case-patients were prevented.

Conclusion: We observed a reduction in measles incidence following the nationwide mass vaccination campaign even though it was conducted approximately one year after the outbreak started. A booster dose at school entry may be of value given the high incidence in persons >5 years.