Emphasising herd immunity in vaccine advocacy: a systematic review and meta-analysis

Abstract

Emphasising herd immunity in vaccine communication may affect vaccine uptake by eliciting prosocial or selfish motivations. While experimental evidence has accumulated, quantitative syntheses are lacking. We conducted a systematic review and three-level meta-analysis to estimate how emphasising herd immunity affects vaccination motivation. Literature up to April 2025 was searched across seven databases (CINAHL, Cochrane Library, Google Scholar, PsycINFO, PubMed, Scopus, Web of Science) without restrictions. Non-experimental studies or those not assessing vaccination motivation were excluded. Risk of bias was assessed using JBI checklists. From 5,862 records, 3,676 underwent title/abstract screening; 278 were assessed, yielding 43 included studies (67 effects), totalling 101,720 participants (51,725 vs. 49,995 for intervention vs. control groups). The pooled effect size (Hedges g = 0.12, 95% CI [0.08, 0.17], p