Evaluation of a school-based measles vaccination screening and catch-up program in Zambia: a mixed methods study

School-based vaccination screening is a promising platform to identify and vaccinate older children missed by routine services. In 2024, Zambia’s Ministry of Health and Ministry of Education implemented a pilot school-based vaccination screening and catch-up (SVS) program in 20 schools across one urban and one rural district, supported by our research team. We conducted an explanatory sequential mixed-methods process evaluation to assess reach, fidelity, effectiveness, feasibility, acceptability and sustainability using the Consolidated Framework for Implementation Research and Proctor et al.’s implementation outcomes. Between June–November 2024 we undertook document review, implementation strength assessment surveys, direct observations and in-depth interviews with implementers and caregivers. Quantitative indicators were summarized descriptively, and qualitative data were thematically analyzed and triangulated across components.Of 4,092 enrolled learners, 81.9% were screened and 77.1% presented vaccination cards. Among those screened, 6.4% missed both measles-rubella (MR) doses and 13.7% missed only MR2. Catch-up uptake was high: 98.1% of MR zero-dose learners received MR1 and 95% of those missing MR2 received catch-up vaccination. Key implementation enablers included strong teacher-nurse coordination, high training participation, the perception of schools as convenient and efficient platforms for SVS activities and the flexibility to adapt community sensitization strategies to local contexts. However, operational constraints included transport limitations, short training duration and burdensome documentation.Zambia’s SVS pilot was feasible, acceptable, and implemented with high reach and uptake through school-based measles screening and catch-up.  Future scale-up would require a national catch-up policy for children older than 5 years, clear operational guidance, and evidence on costs and sustainability. With these in place, SVS could be integrated into school health programs to reach children missing measles doses.