Implementing RED/REC to Reach Zero-Dose Children in Zambia: A CFIR-Informed, Qualitative Study of Barriers and Facilitators

Background: Childhood immunisation coverage remains suboptimal in Zambia, with persistent inequities, particularly among zero-dose and hard-to-reach populations. The Reaching Every District/Reaching Every Child (RED/REC) strategy was developed to strengthen equitable vaccine delivery and improve access to immunisation services. This study explored the barriers and facilitators influencing implementation of RED/REC components in selected zero-dose districts in Zambia. Methodology: An exploratory, descriptive qualitative study was conducted in 2025; of the 127 interviews, 36 were key informant interviews (KIIs), 42 were in-depth interviews (IDIs), and 49 were focus group discussions (FGDs) conducted with caregivers, health workers, community volunteers and programme officers. The data were analysed manually using an abductive thematic approach guided by the Consolidated Framework for Implementation Research (CFIR). Results: Implementation of RED/REC was facilitated by structured microplanning, community mapping, multidisciplinary coordination, outreach services, community engagement and the use of local data to identify and reach zero-dose and under-immunised children. Community-based volunteers and local leaders were particularly important for mobilisation and follow-up. However, implementation was constrained by staff shortages, inadequate transport and outreach infrastructure, limited refresher training, insufficient volunteer incentives, and weaknesses in data tools and capacity. Geographical barriers, seasonal farming and fishing activities, religious beliefs, misinformation and concerns about vaccine adverse effects further affected outreach and uptake. CFIR demonstrated that these barriers and facilitators operated across the Inner Setting, Outer Setting, Characteristics of Individuals and Implementation Process domains. Conclusion: RED/REC provides an interconnected platform for reaching zero-dose and under-immunised children, but effective implementation requires simultaneous strengthening of workforce capacity, outreach resources, community partnerships and data systems. Addressing geographical, seasonal and vaccine-confidence barriers is essential for sustaining implementation and improving equitable immunisation coverage.