Understanding low COVID-19 booster uptake among US adults

Background: Vaccinations against SARS-CoV-2 have consistently been shown to reduce the risk of severe COVID-19 disease. However, uptake of boosters has stalled in the United States at less than 20% of the eligible population. The objective of this study was to assess the reasons for not having obtained a bivalent booster within an existing COVID-19 cohort. Methods: A total of 2196 adult participants from the Arizona CoVHORT, a population-based cohort in the United States established in May 2020, who had received at least one dose of the COVID-19 vaccine, responded to surveys administered between February 13 and March 29, 2023 querying receipt of a bivalent booster and if not, the reasons for not receiving it. Descriptive statistics were employed, including frequencies of responses by participant characteristics, and multivariable logistic regression was used to assess the association between participant characteristics and selected themes for not having received the bivalent booster. Results: The most commonly reported reason for not having been boosted was a prior SARS-CoV-2 infection (39.5%), followed by concern about vaccine side effects (31.5%), believing that the booster would not provide additional protection over the vaccines already received (28.6%), and concern about booster safety (23.4%) or that it would not protect from SARS-CoV-2 infection (23.1%). For themes related to reasons for not having been boosted, those 60 years of age or older were less likely to select items related to knowledge (OR: 0.24; 95% CI: 0.11-0.55) or logistical concerns (OR: 0.09; 95% CI: 0.03-0.30) about the vaccine; while those reporting Hispanic ethnicity were more likely to convey concerns about logistics than those reporting non-Hispanic ethnicity (OR: 2.15; 95% CI: 1.08-4.30). Finally, compared to college graduates, those with some college or technical school were significantly more likely to select items related to the risks and benefits of the bivalent vaccine not being clear as reasons for not having been boosted (OR: 2.41; 95% CI: 1.69-3.43). Conclusions: Improvement in booster uptake is necessary for optimal public health in the United States. The development of vaccines against SARS-CoV-2 occurred at an unprecedented speed, but vaccine uptake remains among the greatest current public health challenges as updated boosters continue to be developed and made available to the public. Interventions to improve vaccination rates require a variety of approaches.