Assessing the effectiveness of school-based vaccination checks to identify and reach un – and under–vaccinated students in Zambia

BACKGROUND: Measles supplementary immunization activities (SIAs) help close immunity gaps but are resource-intensive and may not effectively reach school-aged children who miss routine vaccination. School-based vaccination screening may offer a complementary platform, yet evidence from low- and middle-income countries (LMICs) is limited. This study evaluated the feasibility and effectiveness of school-based vaccination screening and catch-up vaccination in Zambia. METHODS: A pilot intervention was conducted in 10 public and community primary schools in two urban districts (Ndola and Lusaka). Grade 1 learners were screened for routine vaccination status using under-5 cards or caregiver recall. Learners missing doses of oral poliovirus vaccine (OPV), diphtheria-tetanus-pertussis vaccine (DTP), or measles-containing vaccine (MCV) were referred for catch-up vaccination at health facilities or through school-based outreach. Descriptive and regression analyses assessed coverage, under-vaccination, catch-up uptake, and associated factors. RESULTS: Of 1839 learners screened (98% participation), 38.0% were under-vaccinated and 1.8% were zero-dose. MCV2 coverage was lowest (65.6%) and declined with age. Among 699 under-vaccinated learners, 68.7% received at least one catch-up dose, mostly through school-based activities. Under-vaccination was associated with older age, accompaniment by a non-biological respondent, and low maternal education. Missed catch-up vaccination was associated with longer travel time, lack of an under-5 card, and caregiver unwillingness to accept school vaccination. Post-catch-up coverage increased to 96.6% for MCV1 and 83.5% for MCV2. CONCLUSIONS: School-based vaccination screening was feasible, well-accepted, and substantially improved measles vaccination coverage. Scale-up should emphasize timely catch-up delivery, improved record-keeping and coordinated school-health planning. Future operational studies must assess the use of Early Childhood Learning (ECL) classes to reach children at younger ages.