Community engagement for vaccine delivery in low- and middle-income countries and humanitarian settings: A scoping umbrella review

Community engagement (CE) is increasingly recognized as a critical strategy for enhancing vaccine delivery in low- and middle-income countries (LMICs) and humanitarian settings, yet the evidence base remains fragmented. This scoping umbrella review synthesizes findings from 24 reviews published between 2013 and 2024, spanning 56 countries, and addressing both routine and outbreak vaccination efforts. CE interventions were found to be consistently associated with improved vaccine acceptance, reduced hesitancy, and increased coverage, particularly in marginalized and hard-to-reach populations. Key mechanisms of success included community participation, two-way communication, local capacity strengthening, and culturally tailored education and outreach efforts. Trusted local actors played a pivotal role in promoting vaccine uptake by addressing misinformation and fostering trust. Interventions involving school- and home-based delivery, mobile technologies, and integrated strategies combining multiple CE components demonstrated the greatest effectiveness. Despite this, substantial definitional ambiguity around CE persists, leading to variation in implementation and evaluation. The review highlights the need for standardized frameworks to define, design, and assess CE in vaccine programs, emphasizing the importance of context-specific adaptation and inclusivity. Moreover, while CE is widely promoted, few studies explored its limitations or cost-effectiveness. In crisis-affected settings, where time and resources are constrained, early, targeted engagement with key community representatives can still foster local ownership and impact. CE must be understood not as an optional add-on, but as a core element of effective, equitable vaccination strategies. Future research should prioritize the development of operational definitions, theories of change, and robust evaluation tools to optimize CE’s impact on immunization outcomes.