Disentangling the rural-urban immunization coverage disparity in The Gambia: A Fairlie decomposition

Exploring factors underlying disparities in immunization uptake is highly relevant and can contribute to improved immunization interventions globally. The Gambia is an interesting case, since higher immunization coverage in rural areas has been shown for many years, yet the factors explaining this unexpected rural-urban disparity have not been studied. The aim of our study was to quantify the rural-urban disparity in immunization coverage and identify factors that contribute to explaining it.

Data from the nationally representative Demographic and Health Survey 2013 was used to select children aged 12-23 months (Weighted n = 1644) for the study. The outcome measure was full immunization status, the grouping variable was area of residence. Descriptive statistics were used to analyze the proportions of full immunization and rural-urban residence across the exposure variables. The Fairlie decomposition technique was used to decompose factors contributing to explaining the coverage disparity.

The findings show that there is a disparity of 16.06 percentage points to the advantage of the rural areas and the exposure variables explained 76.49% of the disparity. Material factors explained 92.03% of the explained disparity with maternal occupation and household wealth quintile being the only significant individual material variable contributors to the explained disparity. Lower household wealth quintile and working especially in agriculture were associated with higher immunization coverage and they were more common in rural areas. Religion and mother's age group e each contributed somewhat to the explained inequality.

There was a large immunization coverage disparity between rural and urban areas in The Gambia. This disparity was mainly explained by mothers working in agriculture and living in the poorest households, being more likely to immunize their children - unexpected findings. Our study showed that the drivers of healthcare disparities differ by setting and deserve more research.