Summary of aggregated data used in analyses.

Measles & Rubella (MR) zero-dose children (unvaccinated for measles–rubella) cluster in underserved communities can sustain measles transmission. We estimated MR zero-dose prevalence after Zambia’s 2024 MR Supplementary Immunisation Activity (SIA) and identified associated risk factors and barriers. A coverage survey (two-stage stratified cluster design) across all 10 provinces, was conducted from 27th December 2024–16th January 2025, involved interviewing caregivers of children aged 9–59 months; vaccination status was verified by card (11.7%) or recall (88.3%). Data were analysed using survey-weighted methods and logistic regression, adjusting for stratification, clustering, and sampling weights. Among 8,634 children, MR zero-dose prevalence was 11.97% (95% CI: 11.03–12.91), highest in Central (19.15%) and Western (17.71%), lowest in Copperbelt (6.69%). Urban residence reduced odds by 24% vs. rural (aOR 0.76, 95% CI: 0.63–0.92). Risks rose with age (>36 months: aOR 1.60, 95% CI: 1.27–2.00), maternal absence (aOR 1.74, 95% CI: 1.33–2.27), or death (aOR 2.40, 95% CI: 1.23–4.68). Most zero-dose children (88.75%) lacked other vaccines, indicating systemic gaps. Key barriers included unawareness (42.58%) and travel time (>2 hours: aOR 3.20, 95% CI: 1.43–7.16). Nearly one in eight Zambian children remained MR zero-dose post-2024 SIA, concentrated in rural, high-prevalence areas, older children, and motherless households. Priorities include health worker-led awareness campaigns, mobile services to cut travel time, and integrated SIA-Routine Immunisation (RI) strategies (microplanning, tracing, catch-up) to address systemic gaps, supporting global measles elimination under Immunisation Agenda 2030.