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Aim: This thesis aimed to identify potential targets that can be leveraged to enhance vaccination coverage and urban-rural equity, and to evaluate the impact of large-scale interventions on coverage and urban-rural equity in The Gambia.

Methods: This study consists of four quantitative substudies. The data sources used were The Gambian Demographic and Health Survey (2013: n = 1,660; 2020: n = 1,456); an electronic register (n = 41,720 from 2019 to 2020); and a paper-based register (n = 16,972 from 2019 to 2020 and n = 61,839 from 2021 to 2022). The main outcome variables were full basic vaccination and Hepatitis B birth dose timeliness among children aged 12–23 months. The analysis methods used were counterfactual, decomposition, multilevel, difference-in-differences, and controlled interrupted time series analysis.

Findings: Potential targets: missed vaccination opportunities lowered vaccination by more than 10% and explained almost all (95%) of the urban-rural inequity among children who had missed opportunities. Children with delayed or non-vaccinated history, due for vaccination in the third quarter, or vaccinated in private facilities had higher odds of under-vaccination while those vaccinated in more than facility or in facilities with a birth dose-to-health worker ratio of 100–299 had lower odds. Impact of interventions: vaccination coverage improvement was lower (12%) but inequity decreased more in regions that implemented the pay-for-performance scheme. The Hepatitis B birth dose intervention led to a small (2.1%) improvement in timely Hepatitis B vaccination at birth, especially in facilities with the worst performance at baseline.

Conclusions: This thesis has identified several potential targets for improving the vaccination gap. Intervening in the identified factors with consideration for their differential impact in urban and rural areas could improve vaccination coverage and equity in The Gambia and contribute to achieving global vaccination goals. The thesis highlighted the impact of two interventions. However, it does not attribute the improvements in coverage to the pay-for-performance scheme but suggests that it might have contributed to reducing urban-rural inequity. Given the intervention’s impact, the Hepatitis B birth dose intervention alone is insufficient to drive timeliness to the desired 90% coverage for elimination.