ST. LOUIS — Covid-19 vaccines continue to significantly reduce the risk of serious illness and death — particularly for people ages 65 and older — according to a large new study of U.S. veterans.
The research, published Wednesday in the New England Journal of Medicine, found the latest Covid boosters remain comparable in effectiveness to seasonal flu shots.
Vaccines Cut Deaths by 64% in Veterans Study
Researchers from the VA St. Louis Healthcare System analyzed medical records from nearly 300,000 veterans. They found last season’s Covid vaccines reduced the risk of emergency room visits by 29%, hospitalizations by 39%, and deaths by 64% across all age groups.
Overall, the combined vaccine effectiveness was 28% — similar to the annual flu vaccine’s 30% to 60% range.
The study examined outcomes for about 164,000 veterans who received both the Moderna or Pfizer Covid shot and a flu shot last fall, compared with 130,000 who received only the flu shot. Participants were monitored for six months to measure the vaccine’s protection against emergency care, hospitalization, and death.
Older Adults See Greatest Benefit
While all ages saw some protection, benefits were strongest among older adults and people with chronic conditions, such as heart or lung disease.
Among veterans under 65, Covid vaccination reduced serious illness and death by about 27%, while protection jumped to nearly 40% for those 65 and older.
Dr. Michael Mina, an immunologist and former Harvard epidemiologist, said the findings showed “pretty modest benefits” overall, but noted the results were in line with expectations given widespread existing immunity.
“Each person, especially younger adults, should have a discussion with their doctor,” Mina said. “Do they have heart disease, chronic lung issues, or other risks that make vaccination more worthwhile?”
Measuring Protection in a Changing Landscape
Bill Hanage, a professor of epidemiology at the Harvard T.H. Chan School of Public Health, said that with most Americans now carrying some form of immunity from prior infection or vaccination, gauging vaccine effectiveness has become increasingly complex.
“The core message is that even now, with all this background immunity, there’s still a measurable benefit,” Hanage said. “That’s important, especially for the older population, where hospitalizations and deaths can spike during surges.”
Dr. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, praised the study’s design.
“If I can reduce my risk of dying from Covid by 64%, I’m getting that booster,” he said, emphasizing that small percentages translate to large-scale benefits when applied to millions of people.
Waning Protection but Ongoing Impact
Consistent with previous research, the study found vaccine effectiveness waned over six months. Over that period, the vaccines prevented roughly 18 emergency room visits, seven hospitalizations, and two deaths per 10,000 vaccinated people.
Researchers said this modest difference reflects the reduced severity of recent Covid strains but warned that seasonal surges could still strain health systems.
“If you multiply modest protection across millions, you’re preventing thousands of serious cases,” said Dr. Peter Chin-Hong, an infectious disease specialist at the University of California, San Francisco. “That matters — not just for individuals but for hospitals and communities.”
Confusion Over Covid Vaccine Guidance
The study’s findings align with Centers for Disease Control and Prevention (CDC) guidance, which strongly recommends Covid boosters for adults 65 and older and suggests that younger adults consult healthcare providers before getting vaccinated.
Still, the evolving recommendations have caused confusion. Dr. Marty Makary, the Food and Drug Administration commissioner, recently argued that more data are needed on the benefits for young, healthy adults. The CDC maintains that vaccination remains most beneficial for people at increased risk of severe illness.
Messaging Challenges and Vaccine Uptake
Hanage warned that mixed messages could discourage vaccination among older adults — the very group that benefits most. “The current messaging isn’t helping uptake,” he said. “Even in older populations, vaccination rates are already far too low.”
According to CDC data, fewer than half of adults 65 and older typically receive updated Covid shots. Chin-Hong said the best approach is individual consultation: “When young, healthy people ask whether they should get boosted, my advice is simple — talk to your doctor. It’s about understanding your personal risk.”
