Sustainable immunization system design in sub-Saharan Africa

Since their inception in the 1970s, immunization programs have succeeded in drastically reducing under-five mortality, improving health equity, and contributing to 14 of the 17 sustainable development goals. In sub-Saharan Africa, however, vaccination coverage rates have been stagnating in recent years,  and environmental and economic challenges threaten the sustainability of current immunization systems. In addition, vaccine hesitancy and disruptive events such as the covid-19 pandemic challenge the resilience of immunization systems. Based on a broad, transdisciplinary literature review we investigate on the one hand the links between immunization and the SDGs and on the other hand the existing models capable of capturing the complexities of immunization systems. Subsequently, we propose a conceptual systems-inspired model that frames the core elements of both planned and emergency immunization, as a tool for problem structuring and stakeholder engagement. As a next step, based on the Rwandese immunization system, we develop a quantitative, community-level system dynamics model to support sustainable immunization system design. Finally, we formulate summarized conclusions with respect to the design and modeling of immunization systems together with some recommendations for future research directions.