OBJECTIVES: To combat the COVID-19 pandemic, vaccination of the population is essential. However, attitudes regarding vaccination can range from full acceptance to absolute refusal. Vaccination hesitancy is complex and context-specific, varying across pandemic phases, country, sociodemographic characteristics, and vaccines. Evidence-based strategies to address vaccine hesitancy behavior are needed. The aim of this systematic review is to identify and assess the effectiveness of strategies in addressing vaccine hesitancy in adults.

METHODS: A systematic literature review was conducted in PubMed, Embase, and PsycInfo (2016-2021) building on Jarret´s et al. (2015) review. The review adheres to PRISMA guidelines and uses the Cochrane Risk of Bias Assessment Tool. For data analysis, interventions were categorized into: 1) dialogue-based; 2) educational; 3) incentive-based; 4) recall-based; and 5) multi-component interventions. Outcomes of included interventions were categorized into vaccination coverage rate and behavioral outcomes.

RESULTS: Out of 5,023 retrieved studies, six were included in the review in addition to one study from Jarret´s et al. review and three studies from snowballing. All studies focused on influenza vaccine except one which focused on Hepatitis B. Five studies evaluated educational interventions, two dialogue-based interventions, and three multi-component interventions. Multi-component interventions had a significant effect in increasing the vaccination rate (6.5% to 10.2%). Educational interventions had a positive effect in behavioral outcomes. Comparability of studies was limited due to the heterogeneity in study outcome(s), study designs and target populations.

CONCLUSIONS: This review has shown statistically significant results of different strategies in increasing the knowledge and vaccination rates in adults. In a next step, our findings should be contrasted with interventions that may have been implemented during the COVID-19 pandemic to increase vaccination rates. In addition, research is needed to better understand the determinants of vaccine hesitant behavior, which might involve trust in the healthcare system or governmental institutions and their capability to design adequate interventions.