Abstract
BACKGROUND: Designing effective immunization programs requires a strong understanding of how the factors affecting vaccine uptake interplay. In this review, we analyze the relationships between the Behavioral and Social Drivers (BeSD) of routine immunization using qualitative systems mapping (QSM). METHODS: In this review, we analyzed 92 experimental and quasi-experimental impact evaluations (IEs) from 11 LMICs that were published between 2010 and 2020. Secondary literature on the study context or the intervention was also included. The WHO's behavioral and social determinants (BeSD) framework was used to code the determinants identified in these IEs, and their relationships were mapped using qualitative systems mapping. We computed the in-degree (influenced by other determinants) and out-degree scores (influencing other determinants) to assess the extent of the influence of the BeSD determinants on one another. RESULTS: The results identified that knowledge regarding immunization, trust in the health system and quality of immunization services, and community engagement by the health workers was influenced by several other determinants and had a high in-degree score. Caregivers perceptions of quality of immunization services, health provider availability, religious leaders, community engagement by health workers, and physical accessibility had a high out-degree score. We also identified two feedback loops between health provider availability and physical accessibility, and trust and perceptions of immunization quality. CONCLUSIONS: QSM analysis shows that the determinants of immunization uptake were interlinked with each other in complex ways. Our research identified BeSD drivers that affected multiple factors and can be viewed as key leverage points. Programs for improving vaccination uptake need to account for the strong role that caregivers' experience of immunization services and their trust in the health system play in indirectly affecting immunization uptake. There is also a need to acknowledge that fear of vaccination is fear of the opportunity and monetary costs associated with vaccine side-effects. The results from this review can inform discussion and form the basis for context specific research on the factors affecting immunization.