The effect of substance use disorders on vaccine uptake, acceptance, and adherence: a global systematic review

Background: Beyond vulnerabilities that increase susceptibility to infectious disease, people with addictive disorders suffer from unique individual and systemic barriers to accessing treatment. Among these multifaceted barriers, vaccine hesitancy is increasingly recognized as a health challenge affecting populations worldwide. This systematic review aims to evaluate whether people with alcohol, substance use disorders and/or behavioral addictions are less prone to adhere to vaccination recommendations. Authors analyzed the potential reasons underlying the differences in vaccine-related outcomes.

Methods: Electronic searches of published original research articles and reviews were conducted in PubMed, EMBASE, Scopus, and PsycINFO from database inception to December 5th, 2022. Our strategy encompassed retrievals regardless of languages and date of publication. Animal studies, abstracts without a full manuscript, and studies which were considered to have lower robustness of scientific evidence were excluded. Outcomes measured were vaccine uptake, hesitancy, and adherence.

Results: The search yielded 1,208 retrievals of which 103 satisfied our inclusion criteria. The sum encompassed data collected on 5,576,374 persons who were predominantly residents of Europe (n=39) and North America (n=27). Most papers evaluated smoking tobacco (n=91). There was also a focus on other substances such as alcohol (n=11) as well as specific routes of administration (Intravenous drug use; n=10). Studies largely evaluated influenza vaccines (n=96), followed by COVID-19 (n=19) and pneumococcal vaccines (n=10). Tobacco use, the substance for which a large number of studies was identified, was significantly associated with poorer vaccine-related outcomes, particularly influenza, COVID-19, human papillomavirus, maternal and childhood vaccines.

Conclusions: Collectively, the studies identified several groups with statistically significant suboptimal vaccine-related outcomes among whom targeted measures could be beneficial. Timely evidence, especially on behavioral addictions and substances other than tobacco, is lacking and warrants urgent attention. Findings can serve clinicians and policy makers to improve global vaccine coverage among this vulnerable sub-population.