The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines used in the Veterans Affairs (VA) health system are effective for preventing infection, according to a study published online July 20 in the Annals of Internal Medicine.

Adeel A. Butt, M.B.B.S., from the VA Pittsburgh Healthcare System, and colleagues examined the short-term effectiveness of vaccines (BNT162b2 or mRNA-1273) in preventing SARS-CoV-2 infection in the U.S. Department of Veteran Affairs health care system. Data were included for 54,360 persons who tested positive for SARS-CoV-2 infection between Dec. 15, 2020, and March 4, 2021, and 54,360 propensity score-matched controls.

The researchers found that 18.0 percent of those who tested positive and 32.8 percent of those who tested negative had been vaccinated. At seven or more days after the second dose, vaccine effectiveness was 97.1 percent. Effectiveness was 96.2 and 98.2 percent for the Pfizer-BioNTech BNT162b2 and Moderna mRNA-1273 vaccines, respectively. Regardless of age group, sex, race, or presence of comorbidities, effectiveness remained above 95 percent.

"Veterans are at particularly high risk given their older age and greater burden of comorbidities compared with the general population, and the high level of vaccine effectiveness we observed is therefore reassuring," the authors write.

One author disclosed financial ties to Gilead Sciences.