Booster shots from the Pfizer-BioNTech and Moderna vaccines don’t just prevent infections with the contagious Omicron variant — they also keep infected Americans out of hospitalization, according to data published Friday by the Centers for Disease Control and Prevention .
The additional doses are 90 percent effective against hospitalization with the variant, the agency reported. Booster shots also reduced the likelihood of visiting an emergency department or emergency care unit. The additional doses were most effective against infection and death among Americans 50 and older, the data showed.
Overall, the new data shows that the vaccines were more protective against the Delta variant than against Omicron, which lab studies have shown can partially evade the body’s immune response.
It’s generally accepted that booster shots prevent people from getting infected, at least for a while. Data from Israel and other countries has also suggested that boosters may help prevent serious illness and hospitalization, especially in older adults.
“Data from other countries has also shown that getting the booster has a significant benefit, but this really shows it in the US,” Akiko Iwasaki, an immunologist at Yale University, said of the figures released Friday. “These numbers should be very convincing.”
On Thursday evening, the CDC released additional data showing that in December, unvaccinated Americans age 50 and older were about 45 times more likely to be hospitalized than those who were vaccinated and given a third shot.
Yet less than 40 percent of fully vaccinated Americans eligible for a booster shot have received one.
Friday’s results are based on three new studies led by the CDC. In one study, researchers analyzed hospital admissions and visits to emergency rooms and emergency care clinics in 10 states from August 26, 2021 to January 5, 2022.
The vaccine effectiveness against hospitalization with the Omicron variant dropped to just 57 percent in people who received their second dose more than six months earlier, the authors found. A third shot restored that protection to 90 percent.
It’s unclear whether protection from the boosters would also decrease as it did after two shots, noted Natalie Dean, a biostatistician at Emory University.
“We just have to recognize that all of these estimates of Omicron protection against the third dose will be people who have been boosted quite recently,” she said. “We do wonder how sustainable the boosters themselves are.”
While discussing booster shot recommendations for all U.S. adults, scientific advisors to the Food and Drug Administration and the CDC repeatedly complained about the lack of booster shot data specific to the United States.
There are differences between Israel and the United States — for example, in how Israel defines serious illness — that made it challenging to interpret the relevance of Israeli data to Americans, they said.
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Some members of the Biden administration supported the use of booster doses even before the agencies’ scientific advisers had a chance to review the data from Israel. After the arrival of the Omicron variant, federal health officials stepped up their campaign for “boosters for all.”
The CDC now recommends booster shots for anyone ages 12 and older, five months after receiving two doses of the mRNA vaccines made by Pfizer-BioNtech and Moderna, or two months after a single dose of the Johnson & Johnson vaccine. vaccine.
The usefulness of booster shots in Americans under the age of 50 was a topic of fierce debate over the fall. Several experts argued at the time that third injections were not necessary for younger adults because two doses of the vaccine held up well.
Some of those experts were not convinced by the new data.
It was clear even months ago that older adults and those with weakened immune systems would benefit from additional doses of the vaccine, said Dr. Paul Offit, director of the Vaccine Education Center at the Children’s Hospital of Philadelphia and a member of the FDA’s Vaccine Advisory Committee. .
But “where’s the evidence that a third dose benefits a healthy young person?” he asked.
“If you’re trying to stop the spread of this virus, vaccinate the unvaccinated,” he added. “We will continue to try to further protect the already protected people.”
But other experts changed their minds in favor of boosters because of the highly contagious Omicron variant. Even if two doses were enough to keep young people out of hospitals, they said, a third dose could limit the spread of the virus by preventing infections.
“They’re both data-driven, legitimate positions,” said John Moore, a virologist at Weill Cornell Medicine in New York. But at this point, the debate is over: “We’re using boosters in everyone, and that’s what’s happening.”