Coverage and effectiveness of mRNA SARS-CoV-2 vaccines among United States Veterans

Young-Xu, Y.; Korves, C.; Powell, E. I.; Zwain, G. M.; Smith, J.

Importance: The scope of vaccination rollout and effectiveness of mRNA SARS-CoV-2 vaccines in the United States (US), and US Veterans specifically, has not been fully assessed. Objective: To estimate receipt of SARS-CoV-2 vaccines, and vaccine effectiveness (VE) against SARS-CoV-2 infection, subsequent disease-related severity and mortality. Design, Setting, and Participants: First, receipt of any SARS-CoV-2 vaccine by March 7, 2021 was described for all enrolled and alive Veterans within the Veterans Health Administration (VHA). Second, to evaluate mRNA SARS-CoV-2 VE, a matched test negative case-control evaluation was conducted across all VHA facilities utilizing SARS-CoV-2 positive (cases [n=16,690]) and negative (controls [n=61,610]) tests from Veterans aged [≥]18 years old who routinely sought care at a VHA facility and were tested for SARS-CoV-2 from December 14, 2020, through March 14, 2021. Exposures: Vaccination histories were obtained from pharmacy and medical records to determine if patients were unvaccinated, partially vaccinated (from 7 days after first dose until day of second dose of mRNA SARS-CoV-2 vaccine), or fully vaccinated (from 7 days after second dose of mRNA SARS-CoV-2 vaccine) at time of SARS-CoV-2 test. Main Outcome Measures: Primary outcomes were (1) vaccine receipt among Veterans and specific subpopulations, (2) VE calculated from odds ratios (ORs) with 95% confidence intervals (95% CI) for the association between SARS-CoV-2 infection and full vs. no vaccination, and (3) VE against infection for partial vs. no vaccination. VE against COVID-19-related hospitalization and death were also estimated. Results: By March 7, 2020, among 6,170,750 Veterans, 1,547,045 (23.1%) received at least one SARS-CoV-2 vaccine. Based on the analysis of mRNA SARS-CoV-2 vaccines, VE against infection was 93.7% (95% CI 92.0-95.0) and 57.7% (95% CI 53.5-61.5) for full and partial vaccination (vs. no vaccination), respectively. VE was similar for subpopulations. VE against COVID-19-related hospitalization and death for full vs. no vaccination was 90.7% (95% CI 90.0-91.3) and 94.7% (95% CI 91.3-98.1), respectively. Conclusion and Relevance: Vaccines are effective in reducing SARS-CoV-2 infections and disease-related severity and mortality in the Veteran population. Effective vaccine, as well as their efficient and equitable distribution, are important for reducing COVID-19 disease burden among Veterans.