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

Monday, 23rd of June 2014

[source]PLoS One[|source]

There is a dearth of information about the possible causes of recurrent measles outbreaks and little data on the effectiveness of outbreak-response vaccination in African countries. In this report, the authors analyzed the epidemiological characteristics of the 2009 to 2011 measles outbreak and discuss the findings in relation to the measles control practices in the country. In addition, the authors evaluated the effectiveness of the 2010 nationwide periodic supplementary measles vaccination campaign in seven of the nine provinces in South Africa and documented a reduction in measles incidence following the nationwide mass vaccination campaign even though it was conducted nearly one year after the outbreak started. More insights into the lessons learnt are accessible 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.