High-Resolution Geospatial Mapping of Zero-Dose and Underimmunized Children Following Nigeria’s 2021 Multiple Indicator Cluster Survey/National Immunization Coverage Survey

Background
“Zero-dose” children are those who are without any routine vaccination or are lacking the first dose of the diphtheria, tetanus, and pertussis–containing vaccine. Based on global estimates from the World Health Organization/United Nations Children’s Fund in 2022, Nigeria has the highest number of zero-dose children, with >2.3 million unvaccinated. 

Methods
We used data from the 2021 Nigeria Multiple Indicator Cluster Survey/National Immunization Coverage Survey to identify zero-dose and underimmunized children. Geospatial modeling techniques were employed to determine the prevalence of zero-dose children and predict risk areas with underimmunized children at a high resolution (1 × 1 km). 

Results
Zero-dose and underimmunized children are more prevalent in socially deprived groups. Univariate and multivariate bayesian analyses showed positive correlations between the prevalence of zero-dose and underimmunized children and factors such as stunting, contraceptive prevalence, and literacy. The prevalence of zero-dose and underimmunized children varies significantly by region and ethnicity, with higher rates observed in the country’s northern parts. Significant heterogeneity in the distribution of undervaccinated children was observed. 

Conclusions
Nigeria needs to enhance its immunization system and coverage. Geospatial modeling can help deliver vaccines effectively to underserved communities. By adopting this approach, countries can ensure equitable vaccine access and contribute to global vaccination objectives.