Adherence to Planned RED/REC Activities in Six High Zero-Dose Districts of Zambia: A Convergent Mixed-Methods Study

Background: The Reaching Every District/Reaching Every Child (RED/REC) strategy aims to strengthen routine immunization systems and improve equity, but evidence on how consistently planned RED/REC activities are implemented in routine settings remains limited. This study assessed adherence to planned RED/REC activities across six high zero-dose districts in Zambia and explored contextual factors influencing delivery. Methods: We conducted a convergent mixed-methods study in six districts, three predominantly rural and three predominantly urban. The primary quantitative outcome was adherence to planned RED/REC activities, defined as the proportion of planned activities implemented as intended. Adherence was assessed across content, coverage, and frequency. Qualitative data were collected through key informant interviews, in-depth interviews, focus group discussions, and facility observations (94 interviews and discussions with 294 participants). The two strands were integrated and interpreted using Carroll’s conceptual framework for implementation fidelity, with qualitative findings used to explain variation in adherence and the contextual factors shaping delivery. Results: Overall adherence to planned RED/REC activities was high at 83.8% (171/204 facility-indicator observations). Content indicators included regular coordination meetings (87.0%) and defined target populations (81.8%). Coverage indicators were also high, including community volunteer involvement (100%), social mobilization (87.0%), and defaulter tracking (81.8%). Frequency was more variable: 77.3% of facilities met their planned outreach-session target, and recorded supervisory contact was 91.3% for district, 82.6% for provincial, and 65.2% for national officials. Qualitative findings showed that micro-planning, community linkages, and efforts to reach missed children supported implementation. However, continuity of outreach, supervision, and data use was constrained by transport and fuel shortages, staffing limitations, difficult terrain, and inconsistent availability of standard tools. Adaptations such as emergency outreach, service integration, and community volunteer engagement helped sustain delivery. Conclusions: RED/REC was widely implemented, but adherence to planned activities varied across components. Strengthening recurrent operational resources, supervision, data systems, and community-responsive delivery may improve the reliability and equity of implementation. Effects on zero-dose outcomes require further study.