Integrating Behavioral Interventions into the Routine Immunization System in Chad: Implementation Lessons from a Fragile Setting.

Despite global progress, COVID-19 pandemic disruptions increased immunization inequities, particularly in fragile contexts like Chad. In 2022-2023, Chad reported 124,544 zero-dose children, in addition to 122,935 children who were classified as under-vaccinated. Low immunization uptake reflects persistent barriers related to access, knowledge, misinformation, and hesitancy. Behavioral interventions, adapted to low-resource settings, can help address these challenges. Anchored in the WHO Behavioral and Social Drivers (BeSD) framework and aligned with the Immunization Agenda 2030 (IA2030), we designed a multi-partner initiative to build government capacity, strengthen the national immunization system, and integrate a package of culturally grounded behavioral interventions into routine immunization delivery. Partners at the Institut National de la Santé Publique du Tchad (INSAPT), the Ministère de la Santé Publique du Tchad (MSP), Yale University, UT Southwestern, and the Université de N'Djaména co-developed a package of vaccine messages, champions, and reminder-and-recall activities implemented across four field sites. This paper presents a qualitative implementation-focused process evaluation, assessing the feasibility, acceptability, and integration into routine immunization practices. We conducted four site visits at each health center, field observations, and 48 qualitative interviews with community members, health center staff, and MSP staff. Team-based thematic analysis provided key insights into community ownership, integration into daily life, perceived trust, and reported shifts in engagement around vaccination. Participants consistently described the co-creation process and inclusion of active vaccine champions as central to acceptance and participation. Despite early interruption, the initiative highlighted mechanisms through which embedding community-led behavioral interventions within routine immunization systems can support trust, facilitate vaccine engagement, and support IA2030 priorities of locally owned, context-responsive delivery.