Barriers to initial COVID-19 booster among US adults who completed a primary vaccine series in the CHASING COVID cohort, September 2021-October 2022.

It is crucial to understand factors associated with COVID-19 booster uptake in the United States given the updated COVID-19 vaccine recommendations. Using data from a national prospective cohort (n = 4616) between September 2021 and October 2022, we examined socioeconomic, demographic, and behavioral factors of initial booster uptake among participants fully vaccinated with the primary COVID-19 vaccines series. Cox proportional hazards models were used to estimate the associations of each factor with time to initial booster uptake. Most participants (86.5%) reported receiving their initial booster. After adjusting for age, race/ethnicity, education, region, and employment, participants with greater risk for severe COVID-19 had similar booster uptake compared with those with lower risk (adjusted hazard ratio [aHR], 1.04; 95% CI, 0.95-1.14). Participants with greater barriers to healthcare (aHR, 0.89; 95% CI, 0.84-0.96), food insecurity (aHR, 0.82; 95% CI, 0.75-0.89), and housing instability (aHR, 0.81; 95% CI, 0.73-0.90) were less likely to report receiving initial booster compared with those without those barriers. Factors motivating the decision to vaccinate changed from safety-related concerns for the primary series to perceived need for the booster. It is key to address economic and health access barriers to achieve equitable COVID-19 vaccine uptake and continued protection against COVID-19.