The impact of mass vaccination campaigns against polio on under-5 mortality in sub-Saharan countries (2003-2011)

Polio cases worldwide have declined from 60,000 per year in 1980 to <200 today, following repeated mass vaccination campaigns in affected countries. In 2010, 400 Million children worldwide participated in a polio vaccination campaign. Beyond specific effects on polio incidence, such campaigns may reduce under-5 mortality because 1) they can stimulate the demand for other health services, 2) there are potential non-specific effects of the oral Polio vaccine (OPV) on mortality and 3) investments in polio eradication may strengthen health systems. On the other hand, mass vaccination campaigns may also divert scarce human/financial resources from routine services to OPV provision, or foster passive health-seeking behaviors. Despite the scale of the polio eradication initiative, its impact on mortality is unclear because program evaluations have ignored issues of reverse causality. Polio campaigns are indeed more likely to be conducted in areas with limited health seeking behaviors. We devise a new instrumental variable strategy to account for this endogeneity. We use DHS data collected in 8 African countries to construct a time-series dataset on mortality outcomes and campaign exposure spanning 1996-2011. Initial results from 2-stage probit models suggest that polio campaigns reduced the utilization of health services.