Covid booster vaccine offers more protection for adults 65 and older than younger people, new research finds

Covid vaccines continue to protect against serious illness and death, especially for people aged 65 and older, although the benefits for younger adults are not as clear, according to a comprehensive new study of veterans.

Researchers at the VA St. Louis Healthcare System analyzed data from nearly 300,000 veterans and found that last season’s Covid vaccine reduced the risk of emergency room visits by 29%, hospitalizations by 39% and deaths by 64% across all ages.

When the researchers combined the three results, the overall effectiveness was 28%, making the Covid vaccine similar to the annual flu vaccine, which protects 30% to 60% against severe illness or death.

In the new study, published Wednesday in the New England Journal of Medicine, researchers used Department of Veterans Affairs records including about 164,000 people who received the Moderna or Pfizer mRNA Covid vaccine and a flu vaccine at the same time last fall, as well as about 130,000 who received only the seasonal flu vaccine.

Participants were followed for six months to see how effective the Covid vaccines were in preventing emergency room visits, hospitalizations and deaths.

All ages had some protection from vaccination, but the results were more pronounced among older people and those with underlying health conditions, such as heart or lung disease.

For young adults, Covid vaccines provided about 27% protection against emergency room visits, hospitalization or death for people under 65.

For people 65 and older, the overall effectiveness was close to 40%.

The researchers declined to comment on the results.

Dr. Michael Mina, an immunologist and former professor of epidemiology at the Harvard TH Chan School of Public Health, said the study showed “fairly modest benefits” from Covid vaccines, which did not surprise him.

There are limitations to the study. The researchers categorized participants only by ages 65 to 75, over 75, and under 65. Mina said it would have been helpful to see effectiveness in more specific age groups to better determine whether a healthy 25-year-old needs to receive a Covid booster, for example.

“Everyone in certain risk categories, especially younger people, should discuss this with their doctor,” Mina said. “Do they have heart disease? Do they have chronic lung disease? Have they smoked for a long time?”

“A benefit that can still be measured”

Bill Hanage, professor of epidemiology at Harvard TH Chan School, said that because so many people are already immune to Covid, it may be more difficult to identify the vaccine’s effectiveness now. He is nevertheless pleased to see some protection for all age groups.

“The main message is that even today, with all this vaccine-induced immunity and convalescent immunity going around, there is still a measurable benefit,” he said.

Michael Osterholm, an infectious disease expert and director of the Center for Infectious Disease Research and Policy at the University of Minnesota, said the study was well designed and he was encouraged by the results.

“As an older person, I would very happily get my booster dose of this vaccine if I could reduce the risk of dying from Covid by 64%,” Osterholm said.

The vaccine’s effectiveness also declined significantly over the six-month period, consistent with previous research.

The injections prevented 18 emergency room visits, 7 hospitalizations and 2 deaths per 10,000 people vaccinated. The small difference may reflect the decreased severity of a “contemporary” Covid infection, the researchers wrote.

However, a winter surge could still have a measurable impact on society, said Dr. Peter Chin-Hong, an infectious disease physician at the University of California, San Francisco.

“If multiplied by millions of people, even these individual differences, which might be modest, would translate into large numbers of people, which otherwise could strain the health system,” Chin-Hong said.

Confusion over Covid vaccine guidelines

The study results are consistent with updated Centers for Disease Control and Prevention guidelines recommending Covid shots for people 65 and older and only after consulting with doctors or pharmacists.

However, there has been considerable confusion around the new Covid guidelines. People under 65 are not prohibited from getting the Covid vaccine – they still can, although the CDC has said that “the risk-benefit ratio of vaccination in people under 65 is more favorable for those at increased risk of severe disease.”

Food and Drug Administration officials, including its commissioner, Dr. Marty Makary, have recently argued that more data is needed to determine the benefits of Covid vaccination in healthy young adults.

However, Hanage fears that current messaging around vaccines could ultimately have a negative effect on the most vulnerable.

“The message that is being broadcast at the moment does not help vaccination, even in older age groups, which is already far too low,” he said.

Fewer than half of adults ages 65 and older typically receive updated Covid vaccines, according to the CDC.

“No one would argue that it is far more important to ensure that people over 65 have access to vaccines,” Hanage said.

Chin-Hong said that when healthy young people ask him if they should get a booster shot, his advice is simple: Talk to your doctor.