Spatial clustering of measles vaccination coverage among children in sub-Saharan Africa

Tenley K Brownwright,Zan M Dodson,Willem G Van Panhuis

doi:10.1186/s12889-017-4961-9

Tenley K Brownwright, Zan M Dodson + Show 1 more

Open Access

https://doi.org/10.1186/s12889-017-4961-9

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Abstract

BackgroundDuring the past two decades, vaccination programs have greatly reduced global morbidity and mortality due to measles, but recently this progress has stalled. Even in countries that report high vaccination coverage rates, transmission has continued, particularly in spatially clustered subpopulations with low vaccination coverage.MethodsWe examined the spatial heterogeneity of measles vaccination coverage among children aged 12–23 months in ten Sub-Saharan African countries. We used the Anselin Local Moran’s I to estimate clustering of vaccination coverage based on data from Demographic and Health Surveys conducted between 2008 and 2013. We also examined the role of sociodemographic factors to explain clustering of low vaccination.ResultsWe detected 477 spatial clusters with low vaccination coverage, many of which were located in countries with relatively high nationwide vaccination coverage rates such as Zambia and Malawi. We also found clusters in border areas with transient populations. Clustering of low vaccination coverage was related to low health education and limited access to healthcare.ConclusionsSystematically monitoring clustered populations with low vaccination coverage can inform supplemental immunization activities and strengthen elimination programs. Metrics of spatial heterogeneity should be used routinely to determine the success of immunization programs and the risk of disease persistence.

Highlights

During the past two decades, vaccination programs have greatly reduced global morbidity and mortality due to measles, but recently this progress has stalled
Spatial heterogeneity of vaccination coverage can increase the critical vaccination fraction required for herd immunity to a level exceeding the 95% coverage goal set by the Measles-Rubella Initiative [12, 13]
Determinants of low-vaccination clusters We explored possible determinants for clustering of low-vaccination using additional information from country Demographic and Health Surveys (DHS): (1) child in possession of a health card or not (Hc); (2) mother had heard of oral rehydration salts (ORS) or not (O); (3) mother is literate or not (T); (4) mother visited a health facility in the last 12 months or not (Hf ); (5) mother mentioned that money had been a barrier to seeking healthcare in the past or not (M)

Summary

Introduction

During the past two decades, vaccination programs have greatly reduced global morbidity and mortality due to measles, but recently this progress has stalled. The Measles-Rubella Initiative, spearheaded by the American Red Cross, the US Centers for Disease Control and Prevention (CDC), the World Health Organization (WHO), and others, has targeted the measles virus for global elimination. This initiative aims to reduce annual measles incidence rates (IRs) to less than five. The R0 for measles ranges from 15 to 20 infections, which is one of the highest among all infectious diseases (e.g., influenza has an R0 around 1.5–2.0) [7] This high R0 leads to the very high critical vaccination fraction for Brownwright et al BMC Public Health (2017) 17:957 measles of 95%, i.e., the vaccination coverage needed for herd immunity [8]. Spatial heterogeneity of vaccination coverage can increase the critical vaccination fraction required for herd immunity to a level exceeding the 95% coverage goal set by the Measles-Rubella Initiative [12, 13]

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