Critical success factors for high routine immunization performance: A multiple case study analysis of Nepal, Senegal, and Zambia

INTRODUCTION Vaccination averts an estimated 2-3 million deaths annually. Although vaccine coverage improvements across Africa and South Asia have remained relatively stagnant and below global targets, several countries have outperformed their peers with significant increases in routine immunization coverage. Examining these countries’ vaccination programs provides an opportunity to identify and describe critical success factors that may have supported these improvements. METHODS We selected three high-performing countries in regard to childhood vaccination: Nepal, Senegal, and Zambia. This multiple case study analysis was conducted using data from the Exemplars in Vaccine Delivery project within the Exemplars in Global Health program. We used qualitative analysis to investigate factors that contributed to high vaccination coverage through key informant interviews (KIIs) and focus group discussions (FGDs) at the national, regional, district, health facility, and community levels. We triangulated these findings with quantitative analyses using publicly available data, which are published elsewhere. RESULTS Our data revealed that the critical success factors for vaccine programming relied on the cultural, historical, and statutory context in which the interventions were delivered. In Nepal, Senegal, and Zambia, high immunization coverage was driven by 1) strong governance structures and healthy policy environments; 2) adjacent successes in health systems strengthening; 3) government-led community engagement initiatives; and 4) adaptation considering contextual factors at all levels of the health system. CONCLUSION Throughout the study, our analysis returned to the importance of defining and understanding the context, governance, financing, and health systems within a country, rather than focusing on any one intervention. This paper augments findings from existing literature by highlighting how contextual factors impact implementation decisions that have led to improvements in childhood vaccine delivery. Findings from this research may identify transferable lessons and support actionable recommendations to improve national immunization coverage in other settings. What is already known on this topic Immunization is a cost effective and life-saving public health intervention. The essential components of an effective vaccine delivery system are well-established, along with the behaviors related to routine immunization. What this study adds This study highlights how structural and contextual factors impacted the implementation of childhood vaccination programs in several countries with high vaccination coverage. By applying a positive deviant approach, we identify and describe drivers of immunization coverage that programmers and policy makers may utilize to better understand underlying factors within the system. How this study might affect research, practice, or policy Through focusing on countries with high routine immunization coverage, we examined how vaccine delivery systems may leverage components of existing governance structures and health systems to accelerate and sustain coverage. Operational definitions for governance, health systems strengthening, community engagement, and adaptive capacity, along with descriptions of how these processes were implemented in high-performing countries, may help other countries implement similar improvements. ### Competing Interest Statement The authors have declared no competing interest. ### Clinical Protocols ### Funding Statement This work was supported by the Bill & Melinda Gates Foundation, Seattle, WA (OPP1195041) with a planning grant from Gates Ventures, LLC, Kirkland, WA. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study was considered exempt by the Institutional Review Board committee of Emory University, Atlanta, Georgia, USA (IRB00111474); approved by the Nepal Health Research Council (NHRC; Reg. no. 347/2019) in Kathmandu, Nepal; the National Ethical Committee for Health Research (CERNS; Comite National d Ethique pour la Recherche en Sante) in Dakar, Senegal (00000174); the University of Zambia Biomedical Research Ethics Committee (Federal Assurance No. FWA00000338, REF. No. 166-2019); and the National Health Research Authority in Zambia. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). 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