Catching up missed children and reducing missed opportunities for vaccination in Tanzania: insights from a qualitative analysis paired with an EPI review

Introduction: the Expanded Programme on Immunization, initiated by the World Health Organization in 1974, has significantly improved global health by providing equitable access to life-saving vaccines. Despite these achievements, the COVID-19 pandemic caused setbacks in immunization coverage. The Big Catch-Up initiative, launched in April 2023, aims to restore immunization levels by targeting zero-dose and under-immunized children. This study examines BCU integration with routine immunization activities in Tanzania, focusing on the operational dimensions of catch-up efforts, challenges and enabling factors. Methods: a comprehensive EPI review was conducted in November 2024, incorporating catch-up efforts alongside routine immunization components. Structured BCU questionnaires were developed for four levels of the health system: national, regional, district, and health facility personnel. Data collection involved 66 key informant interviews across various geographic areas. Thematic analysis was used to code and analyze qualitative data, utilizing DelveTool for data management and analysis. Results: Tanzania’s early roll-out of the BCU initiative, combined with polio and measles outbreak responses, demonstrated a proactive approach to addressing immunization gaps. Key strengths included well-articulated goals and targets, catch-up vaccination policy availability, and community engagement. Challenges included limited policy dissemination at lower levels, inconsistent recording practices, and staff shortages. Routinization of catch-up vaccination and capacity-building programmes was identified as essential for sustaining immunization efforts. Conclusion: integration of catch-up strategies into routine immunization activities and the proactive approach of the Tanzanian government were key success factors. Structured policy dissemination, robust data management systems, and capacity-building programmes are crucial for demonstrating results, sustaining and expanding immunization efforts.