Date of Award

Summer 2023

Document Type

Open Access Dissertation


Health Services and Policy Management

First Advisor

Nicole L. Hair


Background: Despite continuous efforts to enhance childhood vaccination coverage, a considerable number of children in sub-Saharan Africa (SSA) remain unvaccinated (zero-dose). Recent estimates indicate that approximately 17 million zero-dose children reside mainly in 10 Low- and Middle-Income Countries (LMICs) in SSA. The Immunization Agenda 2030 (IA2030) aims to reduce the number of zero-dose children by half, necessitating research to identify populations and groups at higher risk of being unvaccinated.

Objectives: This research sought to (1) examine individual and contextual factors associated with zero-dose status in SSA, (2) assess the geographical clustering of zero-dose children aged 12-59 months in SSA and the associated sociodemographic characteristics among regions, and (3) evaluate the impact of the Global Vaccine Action Plan (GVAP) policy on the prevalence of zero-dose children in Nigeria.

Methods: The study utilized data from the Demographic and Health Surveys Program and open data repositories. For aims 1 and 2, a pooled cross-sectional study design was employed, including a sample of 133,739 children aged 12–59 months from 33 SSA countries between 2010 and 2020. Multilevel logistic regression was used to analyze factors associated with zero-dose vaccination status (aim 1), while global ordinary least square estimates and multiscale geographically weighted regression (MGWR) were used to examine factors linked to spatial clustering (aim 2). For aim 3, a difference-in-differences (DD) design was used to analyze a sample of 37,278 children aged 12–35 months from three West African countries. Specifically, this analysis involved comparing the changes in zero-dose status between Nigeria and the neighboring countries of Benin and Cameroon over the same specified time period.

Results: Aim 1 revealed that both individual and contextual factors were correlated with zero-dose status in SSA, with 9.1% of children having not received any vaccines. Aim 2 showed high rates of zero-dose children in SSA, with clear evidence of spatial clustering in specific areas associated with sociodemographic factors. Aim 3 demonstrated that the implementation of GVAP policy in Nigeria was linked to a significant reduction in the prevalence of zero-dose children.

Conclusion: This research identified the factors, both individual and contextual, linked to the zero-dose status among children in SSA. Additionally, the study found spatial clustering of zero-dose children across different regions in SSA, influenced by sociodemographic characteristics. Notably, the implementation of the GVAP policy has led to a significant reduction in the prevalence of zero-dose children in Nigeria. These findings underscore the urgency of addressing vaccination disparities in SSA and emphasize the need to incorporate both individual and contextual considerations when designing interventions. The IA2030 goals provide a crucial framework to guide efforts in achieving equitable vaccine coverage. Collaboration among governments, non-governmental organizations, and international bodies is essential to attain these ambitious targets. By gaining a comprehensive understanding of the complexities surrounding zero-dose status and its associated factors, evidence-based strategies can be tailored to effectively reach underserved communities and strive for a healthier, more equitable future for all children in sub-Saharan Africa.


© 2023, Chamberline Ekene Ozigbu

Available for download on Sunday, August 31, 2025