Booster shots of the Pfizer-BioNTech and Moderna vaccines not only reduce the number of infections with the highly contagious variant of Omicron, they also keep infected Americans out of hospitals, according to data released Friday by the Centers. for Disease Control and Prevention. .
Additional doses are 90% effective in preventing hospitalization with the variant, the agency reported. Booster shots also reduce the likelihood of a visit to an emergency department or urgent care clinic. The data also showed that supplemental doses are most beneficial against infection and death in Americans aged 50 and older.
Overall, the new research indicates that vaccines are more protective against the Delta variant than against Omicron, which, according to laboratory studies, is partially able to bypass the body’s immune response.
“These reports add more evidence to the importance of being up to date with Covid vaccinations,” CDC director Dr. Rochelle Walensky said during a White House briefing on Friday.
While data from Israel and other countries suggested that boosters may help prevent serious illness and hospitalization, at least in the elderly, it was not clear that the extra doses would have this effect in the elderly. United States, where vaccination and immunity patterns differ. from those elsewhere in the world.
The three studies released Friday are by far the most comprehensive and reliable assessments of the role booster shots are playing in the U.S. pandemic. The researchers looked at millions of cases, as well as tens of thousands of hospitalizations and deaths, as the Delta and Omicron variants rose to prominence.
“These numbers should be very compelling,” Yale University immunologist Akiko Iwasaki said of the numbers released Friday.
The detailed reports have come in with hints that Omicron’s thrust may be pulling back. The country is reporting 736,000 new cases a day, down from more than 800,000 last week, and hospital admissions have fallen.
Yet the virus continues to spread in many states and more than 2,000 deaths still occur over several days.
Two of the studies were published in the CDC Morbidity and Mortality Report. In one study, researchers analyzed hospitalizations and visits to emergency departments and urgent care clinics in 10 states from August 26, 2021 to January 5, 2022.
Vaccine effectiveness against hospitalization with the Omicron variant fell to just 57% in people who had received their second dose more than six months earlier, the authors found. A third shot restored this protection to 90%.
The second study looked at nearly 10 million Covid cases and more than 117,000 associated deaths recorded across 25 state and local health departments between April 4 and December 25, 2021.
Cases and deaths were lower in people who received a booster dose, compared to those who were fully vaccinated but did not receive a booster, and much lower than the rates seen in unvaccinated people, reported Researchers.
Booster doses provided significantly greater protective gains in people aged 65 and older, followed by those aged 50 to 64, according to the study. The researchers did not provide data on the benefits of the injections in younger people.
In the third study, published in the journal JAMA, data from more than 70,000 people who sought to be tested showed that a third dose offered more protection against symptomatic infection than two doses or none. Full vaccination and boosters were less protective against the Omicron variant than against Delta.
On Thursday evening, the CDC released additional data on its website showing that in December, unvaccinated Americans 50 and older were about 45 times more likely to be hospitalized than those who were vaccinated and received a third vaccine.
Taken together, the studies clearly show that boosters are a valuable defense against Omicron. Yet less than 40% of fully vaccinated Americans who are eligible for a booster received one.
It’s too early to tell whether protection from additional injections might diminish, noted Natalie Dean, a biostatistician at Emory University.
“We just have to recognize that all of these estimates of protection per third dose of Omicron will be for people who have recently been boosted,” she said.
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The CDC now recommends booster shots for anyone 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.
When debating booster recommendations for all US adults, scientific advisers to the Food and Drug Administration and CDC repeatedly lamented the lack of US-specific data.
There are differences between Israel and the United States — for example, in how Israel defines serious illnesses — that have made it difficult to interpret the relevance of Israeli data to Americans, they said.
Some members of the Biden administration have backed the use of booster doses even before the agencies’ scientific advisers had a chance to review Israel’s data. Federal health officials stepped up the campaign of recalls for all after the arrival of the Omicron variant.
The usefulness of booster shots in Americans under 50 was the subject of vigorous debate in the fall. Several experts argued at the time that third shots were not necessary for young adults because two doses of vaccine held together well.
Some of these experts are still unconvinced by the new data.
Even months ago, it was clear that the elderly and those with weakened immune systems would benefit from extra doses of the vaccine, said Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia and member of the FDA Vaccine Advisory Committee. .
But “where is the evidence that a third dose benefits a healthy young person?” He asked.
“If you are trying to stop the spread of this virus, vaccinate the unvaccinated,” he added. “We continue to try to further protect those who are already protected.”
But other experts changed their minds in favor of boosters with the arrival of the highly contagious variant of Omicron. 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.
“These are both legitimate data-driven posts,” said John Moore, a virologist at Weill Cornell Medicine in New York.
But at this point, the debate is over: “We use boosters in everyone, and that’s what happens.”