The effectiveness of nonfinancial interventions and monetary incentives on COVID-19 vaccination: A meta-analysis

Objective: Although mass vaccination is critical for curbing the spread of COVID-19 and saving lives, vaccine rates remain suboptimal in most countries, calling for effective behavioral interventions to promote vaccinations. Nonfinancial behavioral interventions and monetary incentives are commonly used to promote COVID-19 vaccination but their effects are mixed.
Method: Articles were searched in the Web of Science, PubMed, and PsycINFO databases. Previous review papers, Google Scholar search, references from the included articles, and unpublished databases were also searched for any other relevant articles.
Results: Drawing on 71 studies comprising 1,132,533 participants and 233 effect sizes, we found that the overall behavioral interventions (including nonfinancial interventions and monetary incentives) have a small but statistically significant effect size of Cohen's d = 0.20, 95% confidence interval [0.08, 0.31]. Different types of single interventions and combined strategies produce similar effects. Effect sizes were not moderated by early/late implementation time points, except that collective benefit-oriented interventions showed a marginally significant downward trend as COVID-19 evolves. The effect size of nonfinancial interventions did not significantly differ from monetary incentives.
Conclusions: Our findings affirm the value of nonfinancial strategies and may help forecast the effectiveness of future interventions for ever-evolving pandemics.