Introduction Little is known about the factors influencing people making decisions about the COVID-19 booster vaccine given the evolution of the COVID-19 virus, the updated vaccines, and easing of public health restrictions

Our study aims to: (1) identify factors influencing COVID-19 booster vaccine decisions; and (2) determine the decisional needs of people considering the COVID-19 booster vaccine decision.

Methods A systematic review was conducted and reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Eligible studies were conducted with adults who made the COVID-19 booster vaccine decision for themselves and reported the influencing factors or decisional needs. We included qualitative, quantitative, and mixed methods primary studies. Time was limited from December 2019 to the present with no geographic or language limitations.

Five databases were searched: MEDLINE, Embase, Web of Science, PsycINFO and CINAHL. Two reviewers independently conducted the title/abstract and full-text screening using Covidence and extracted data based on the Cochrane checklist including (1) study identification, (2) methods, (3) participant characteristics, (4) data collection tool/measurement instruments, (5) influencing factors, (6) decisional needs. We assessed the quality of the included studies using the Mixed Methods Appraisal Tool. We analyzed the findings descriptively.

Results Of 3565 records identified, 306 full-text studies were screened for eligibility and 150 studies were included. Preliminary analysis identified concerns about COVID-19 infection, vaccine effectiveness and safety, and public health recommendations as the most common factors influencing decisions about COVID-19 booster vaccination. Decisional needs were inadequate knowledge, inadequate support/resources, and unclear values limiting quality decisions.

Discussion Compared to the COVID-19 primary series, new factors influencing booster vaccines were concerns about COVID-19 infection and vaccination history. There are unmet decisional needs for booster vaccines.

Conclusion Interventions to support decision making about COVID-19 booster vaccinations need to address unique decisional needs.