Geospatial Distribution of MMR Vaccination and Incidence in Iraq, 2001-2016

Abstract

The 2003 U.S.-led invasion of Iraq created health system instability, with direct and indirect public health consequences. This analysis examines the disparity in vaccine coverage, incidence, and displacement in Iraq at the governorate level for three vaccine-preventable diseases – measles, mumps, and rubella – between 2001 and 2016 using data from the Iraqi Ministry of Health and annual totals of persons of concern from the United Nations High Commissioner for Refugees. We first performed descriptive analyses to look at the geospatial variation of reported vaccine coverage and disease incidence, identifying large variability in incidence of the three diseases – on the order of 100x for measles - between governorates. In a pooled statistical analysis, using a linear mixed effects regression model, we saw an increase in incident measles cases per 100,000 persons for each additional percent unvaccinated (0.8, 95% CI: [0.4, 1.2], p-value < 0.001). Analyzing governorates individually, the statistically significant estimates varied between 1.6 to 3.7 additional cases per 100,000 persons. When incorporating persons of concern into our pooled regression model, we identified larger measles incidence for every additional 10,000 persons of concern (0.26, 95% CI: [0.19, 0.33], p-value < 0.001), holding vaccine coverage constant. These relationships were not significant for mumps or rubella. In conclusion, we found high variability in the geospatial pattern of MMR vaccine coverage and disease incidence between 2001 and 2016 that was not adequately captured by the national level summary statistics. However, the relationship between incidence and vaccine coverage is complex and complicated by other factors, so we did not expect a consistent association between the two variables.