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Updated booster shot prevents a majority of Covid hospitalizations in older adults

New data from the CDC finds that the booster shot is particularly effective at keeping older adults out of the hospital.
Pharmacist Patricia Pernal administers the COVID-19 vaccine during a clinic for seniors in Chicago
Pharmacist Patricia Pernal administers the Covid-19 vaccine during a clinic for older adults in Chicago on Sept. 9.E. Jason Wambsgans / Tribune News Service via Getty Images file

The updated Covid booster shot is proving to be effective at keeping people — especially older adults — out of the hospital, according to two new studies published Friday by the Centers for Disease Control and Prevention.

The findings come as Covid cases rise amid the holiday season.

"We think that there's likely a surge coming," said Ruth Link-Gelles, who heads the CDC's Covid-19 vaccine effectiveness program. "This is really when you want added protection."

Full coverage of the Covid-19 pandemic

Both studies looked at the impact the updated Covid booster shot has had since it was first recommended by the CDC on Sept. 1. The booster targets the omicron subvariants BA.4 and BA.5 as well as the original coronavirus strain. 

The first study estimated that the boosters are more than 80% effective at preventing hospitalizations in adults ages 65 and up.

This is the first real-world data from U.S. researchers to look at how well the shot fares against hospitalization among older adults.

"These data reinforce that getting booster shots this winter is important for people's health," said study leader Dr. Wesley Self, an infectious diseases expert at Vanderbilt University Medical Center in Nashville, Tennessee.

The analysis included 798 people ages 65 and up, nearly three-quarters of whom had underlying conditions. It was conducted from Sept. 8 to Nov. 30, during which time several omicron subvariants, including BA.5 and the combination of BQ.1 and BQ.1.1, have reigned as the predominant strains.

Those who had received the updated booster were 84% less likely to be hospitalized with Covid, compared with people who had never had the Covid vaccine. The effectiveness was nearly identical — 83% — for people who had their last Covid shot more than a year ago.

"The pandemic is not as severe, fortunately, as it had been in the past," Self said. "But there's still a risk, and these new booster shots do provide a level of protection above what people have if they had just their original vaccines."

Research from the CDC released last month also found that the boosters worked better than previous versions of the vaccine to prevent infections.

Everyone, especially those 65 and older "who are at highest risk for severe Covid-19 illness, should receive a bivalent booster dose as soon as they are eligible and to consider masking in indoor public spaces to maximize protection against Covid-19 hospitalization this winter season," Self and other study authors wrote in the new report.

But booster uptake remains low. "There are 28 million people over the age of 65 that are eligible for this updated booster shot but haven’t gotten it," Link-Gelles said.

According to the latest CDC data, just 35.7% of adults 65 and older have received the booster. Among all adults, the percentage falls to 16%.

The second study, also published Friday by the CDC, found similar benefits. The research, which included data on 93,830 adults 18 and older, found the booster shots to be at least 56% effective against Covid-related visits to emergency departments or urgent care centers and hospitalizations, compared with unvaccinated people.

"That's really what these vaccines are designed to do: keep people out of the hospital," said Link-Gelles, who led that study.

The vaccines, she said, are known to be safe and come with few side effects.

"I'm willing to trade a sore arm and maybe a little bit of fatigue and aches for an evening to keep me out of the hospital. These vaccines are doing that," she said.

Dr. Cameron Wolfe, an infectious disease expert and an associate professor of medicine at the Duke University School of Medicine, said the findings will help him to encourage patients to get the booster shot ahead of holidays like Christmas and New Year's.

"A booster takes seven to 10 days to get its full effect," Wolfe said. "This is a nice, timely reminder if you're planning to travel, congregate or take time off for the holiday. You don't want to derail that by getting Covid."

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