Assessing community vulnerability to reduced vaccine impact in Uganda and Kenya: A spatial data analysis [version 1; peer review: 1 approved with reservations]

Background: Despite global efforts to improve on vaccine impact, many African countries have failed to achieve equitable vaccine benefits. Reduced vaccine impact may arise from interplay between structural, social, and biological factors, that hinder communities from achieving full benefits from vaccination programs. However, the combined influence of these factors to reduced vaccine impact and the spatial distribution of vulnerable communities remains poorly understood. In this work, we developed a Community Vaccine Impact Vulnerability Index (CVIVI) that integrates data on multiple risk factors associated with impaired vaccine impact. The index identifies communities are at risk of reduced vaccine impact, and key factors contributing to their vulnerability.

Methods: Vulnerability indicators were identified through literature review and grouped into structural, social, and biological domains. Using secondary data from Uganda and Kenya, we used percentile rank methodology to construct domain-specific and overall vulnerability indices. Correlation analysis was conducted to explore the relationship between indicators. Geo-spatial techniques were used to classify districts/counties from least to most vulnerable and to generate vulnerability maps.

Results: Our findings revealed distinct geographical distribution of community vulnerability to reduced vaccine impact. In Kenya, the most vulnerable counties were clustered in the northeast and east, including Turkana, Mandera, and West Polot. In Uganda, vulnerability was more scattered, with the most vulnerable districts concentrated in the northeast (such as Amudat, Lamo) and southwest (such as Buliisa and Kyenjojo). Key factors contributing to high vulnerability in these counties/ districts cut across different domains, including long distance to the health facilities, low maternal education, low wealth quintile, high prevalence of malnutrition, limited access to postnatal care services, and limited access to mass media.

Conclusions: The index is a potential tool for identifying vulnerable communities, and underlying causes of vulnerability, which guides the design of tailored strategies to improve vaccine impact among vulnerable communities.