Estimating the effects of interventions on increasing vaccination: systematic review and meta-analysis

As global vaccination rates have reached their lowest point in nearly 15 years, effective interventions are being required globally to promote vaccination; however, there is a lack of rigorous evaluation of the effect of various interventions. Through a global synthesis, we analysed data from approximately 6 125 795 participants across 319 studies in 41 countries to reveal the global landscape of four intervention themes and to assess their effectiveness in increasing vaccination rates. We found an overall positive effect of the interventions across four main themes on improving vaccination. Specifically, dialogue-based interventions increased vaccination rates by 43.1% (95% CI: 29.8 to 57.9%, with effect sizes measured as relative risks (RRs)), though they may not always be effective in adolescents or in the sample with a higher percentage of male participants. Incentive-based interventions, whether implemented alone or combined with other intervention themes, failed to demonstrate a significant effect in children. Reminder/recall-based interventions were also effective for promoting vaccination (38.5% increase, 95% CI: 28.9 to 48.9%), particularly for completing vaccine series. Multi-component interventions exhibited excellent effectiveness in vaccination (54.3% increase, 95% CI: 40.5 to 69.6%), with the combination of dialogue, incentive and reminder/recall proving more effective than other multi-component interventions, but showing no significant effects in populations with high initial vaccination rates. However, we found that in most cases combining additional interventions with a single intervention may not significantly improve their effectiveness, especially for incentive-based interventions, but dialogue-based and reminder/recall-based interventions appear to be beneficial in some specific combinations. These findings underscore the importance of governments, public health officials and advocacy groups implementing appropriate vaccine interventions by selecting interventions tailored to specific populations, strategically promoting the completion of vaccine series and effectively combining interventions to promote global vaccination and save more lives.