COVID-19 vaccines updated last year helped prevent severe illness, including hospitalizations and deaths, according to data from a large study of U.S. military veterans released Wednesday.
Vaccinated veterans who contracted COVID after receiving the 2024-2025 booster shots from Moderna or Pfizer/BioNTech were also less likely to visit the emergency room for complications, compared to unvaccinated patients, researchers report in the journal The New England Journal of Medicine.
Researchers followed 164,132 veterans who simultaneously received a 2024-2025 COVID booster and a flu vaccine, as well as 131,839 people who only received the flu vaccine.
The vast majority of participants were at least 45 years old, and virtually all COVID vaccine recipients received one of two approved messenger RNA vaccines, which have recently been the subject of renewed controversy by U.S. Health Secretary Robert F. Kennedy Jr., who has questioned their safety and effectiveness, contradicting established scientific evidence.
Significant clinical benefit
“Vaccines continue to provide additional — although not perfect — protection against important outcomes, including hospitalization and death, although such serious complications are now much rarer than early in the pandemic,” said Dr. Jesse Goodman of Georgetown Medical Center in Washington, DC, who was not involved in the study.
Over a six-month period, veterans who received the COVID and flu vaccines saw a 29% reduction in emergency room visits, 39% reduction in hospitalizations and 64% reduction in deaths compared to those who received the flu vaccine only.
This trend was true regardless of age or the presence of major chronic illnesses.
In absolute terms, the incremental impact of the COVID vaccine remained modest, in part because circulating virus variants caused milder forms, and previous infections as well as vaccination boosted immunity, the researchers said.
Vaccination made it possible to avoid, according to their estimates, 18.3 visits to the emergency room, 7.5 hospitalizations and 2.2 additional deaths per 10,000 patients.
As the rate of severe illness and COVID-related deaths has fallen sharply over time, the additional protection offered by the vaccine is much less than before, observes Dr. Eric Rubin, editor-in-chief of the NEJM.
“Given the very low risk associated with vaccination in this (middle-aged and older) population, these data suggest that at the time of the study, vaccination remained an attractive option,” Rubin said.
Goodman, former chief scientist at the US Food and Drug Administration, believes that all recent observational studies, including this one, “support that vaccines retain significant effectiveness on major outcomes.”
Vaccine effectiveness appeared to decline slightly during the six months of follow-up, the researchers found.
The authors point out that the study was not a randomized trial and therefore cannot definitively prove that COVID vaccines prevented the most severe forms of the disease.
