Rates of and Factors Associated With Primary and Booster COVID-19 Vaccine Receipt by US Veterans, December 2020 to June 2022

Abstract

Importance: COVID-19 vaccination rates remain suboptimal in the US. Identifying factors associated with vaccination can highlight existing gaps and guide targeted interventions to improve vaccination access and uptake.

Objective: To describe incidence and patient characteristics associated with primary, first booster, and second booster COVID-19 vaccination in the Veterans Health Administration (VHA).

Design, setting, and participants: This retrospective cohort study assessed US veterans receiving care in VHA medical centers and outpatient clinics as of December 1, 2020. All VHA enrollees with an inpatient, outpatient, or telehealth encounter in VHA as well as a primary care physician appointment in the preceding 24 months were included.

Exposures: Demographic characteristics, place of residence, prior SARS-CoV-2 infection, and underlying medical conditions.

Main outcomes and measures: Cumulative incidence of primary, first booster, and second booster COVID-19 vaccination through June 2022. Cox proportional hazards regression was used to identify factors independently associated with COVID-19 vaccination.

Results: Among 5 632 413 veterans included in the study, 5 094 392 (90.4%) were male, the median (IQR) age was 66 (51-74) years, 1 032 334 (18.3%) were Black, 448 714 (8.0%) were Hispanic, and 4 202 173 (74.6%) were White. Through June 2022, cumulative incidences were 69.0% for primary vaccination, 42.9% for first booster, and 9.3% for second booster. Cumulative incidence for primary vaccination increased with increasing age, from 46.9% (95% CI, 46.8%-47.0%) among veterans aged 18 to 49 years to 82.9% (95% CI, 82.8%-83.0%) among veterans aged 80 to 84 years. More Black veterans completed primary vaccination (71.7%; 95% CI, 71.6%-71.8%) compared with White veterans (68.9%; 95% CI, 68.9%-69.0%), and more urban-dwelling veterans completed primary vaccination (70.9%; 95% CI, 70.9%-71.0%) compared with highly rural-dwelling veterans (63.8%; 95% CI, 63.4%-64.1%). Factors independently associated with higher likelihood of both primary and booster vaccination included older age, female sex, Asian or Black race, Hispanic ethnicity, urban residence, and lack of prior SARS-CoV-2 infection.

Conclusions and relevance: In this cohort study of US veterans, COVID-19 vaccination coverage through June 2022 was suboptimal. Primary vaccination can be improved among younger, rural-dwelling veterans. Greater uptake of booster vaccination among all veterans is needed.

Conflict of interest statement

Conflict of Interest Disclosures: Dr Maciejewski reported owning stock in Amgen due to spouse's employment. Dr O'Hare reported receiving grants from the National Institutes of Health, personal fees from the University of California, San Francisco, National Kidney Foundation Northern California, and personal fees from JAMA Internal Medicine outside the submitted work. Dr Viglianti reported receiving grants from the National Heart, Lung, and Blood Institute of the National Institutes of Health during the conduct of the study. Dr Hynes reported receiving grants from the VA during the conduct of the study and salary from Oregon State University outside the submitted work. No other disclosures were reported.

Figures

Figure 1.. Percentage of US Veterans With No Receipt and Receipt of Primary and Booster Vaccination for COVID-19 as of June 30, 2022, Overall and by Age Group

Age was determined in March 2022, when the US Food and Drug Administration authorized a second booster vaccination for persons 50 years or older.

Figure 2.. Cumulative Incidence of COVID-19 Primary Vaccination Among US Veterans, December 1, 2020, to June 30, 2022

Figure 3.. Cumulative Incidence of COVID-19 First Booster Vaccination Among US Veterans, September 1, 2021, to June 30, 2022

Figure 4.. Cumulative Incidence of COVID-19 Second Booster Vaccination Among US Veterans, March 1, 2022, to June 30, 2022