Strategies for improving childhood routine immunization coverage: a global systematic review & meta-analyses

Abstract Childhood vaccination is one of the most effective public health interventions, yet in 2024 an estimated 14.3 million children under five remained unvaccinated. Identifying strategies to close this coverage gap is critical to reducing vaccine-preventable disease burden. This systematic review synthesized global evidence on strategies to improve childhood routine immunization coverage. We searched MEDLINE, EMBASE, PsycINFO, and CINAHL, complemented by citation searches, for randomized controlled trials, cluster randomized trials, and controlled before–after studies. Following screening of 3,251 citations, 35 studies were included. Data were extracted, risk of bias was assessed, and strategies were evaluated using meta-analysis and narrative synthesis. Twenty-eight distinct strategies were identified. Among these, a limited subset demonstrated consistent positive effects supported by low or some risk of bias and moderate certainty. Conditional and unconditional cash transfers yielded small but statistically significant improvements in full vaccination coverage (pooled RR: 1.11; 95% CI: 1.07–1.15; I² = 0%; 2 studies), while home-based identification and outreach strategies showed small-to-moderate gains (median RR: 1.23; IQR: 1.09–1.37; 2 randomized studies). Informational vaccination sessions, delivered at facilities or in homes, demonstrated meaningful improvements for key outcomes such as DTP-3 (pooled RR: 1.33; 95% CI: 1.03–1.62; 2 studies). Overall, most strategies produced incremental gains in vaccination coverage, with effectiveness varying by context, delivery model, and vaccination stage. Progress toward the Immunization Agenda 2030 will depend on scaling reliable, system-compatible strategies, tailoring implementation to local health systems, and prioritizing approaches with consistent benefits and appropriate certainty.