Booster shots of the
Pfizer-BioNTech and Moderna vaccines are
not just preventing infections with the contagious omicron variant — they are
also keeping infected Americans from ending up in the hospital, according to
data published Friday by the Centers for Disease Control and Prevention.
اضافة اعلان
The extra doses are 90% effective against hospitalization with
the variant, the agency reported. Booster shots also reduced the likelihood of
a visit to an emergency department or urgent care clinic. The extra doses were
most effective against infection and death among Americans 50 and older, the
data showed.
Overall, the new data show that the vaccines were more protective
against the delta variant than against omicron, which lab studies have found is
partially able to sidestep the body’s immune response.
It is generally accepted that booster shots keep people from
becoming infected, at least for a while. Data from Israel and other countries
have also suggested that boosters can help prevent severe illness and
hospitalization, especially in older adults.
“Data from other countries have also shown significant benefit
of getting the booster, but this is really showing it in the U.S.,” Akiko
Iwasaki, an immunologist at Yale University, said of the figures released
Friday. “These numbers should be very convincing.”
On Thursday night, the CDC published additional data showing
that in December, unvaccinated Americans 50 and older were about 45 times more
likely to be hospitalized than those who were vaccinated and got a third shot.
Yet less than 40% of fully vaccinated Americans who are 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 hospitalizations and visits to emergency
departments and urgent care clinics in 10 states from Aug. 26, 2021 to Jan. 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 that protection to
90%.
It is unclear whether protection from the boosters might also
wane as it did after two shots, noted Natalie Dean, a biostatistician at Emory
University.
“We just have to recognize that all these estimates of omicron
third-dose protection are going to be people who are pretty recently boosted,”
she said. “We do wonder the durability of boosters themselves.”
When debating booster shot recommendations for all American
adults, scientific advisers to the Food and Drug Administration and the CDC
repeatedly bemoaned the lack of booster shot data that was specific to the
United States.
There are differences between Israel and the United States — for
example, in the way Israel defines severe illness — that made it challenging to
interpret the relevance of Israeli data for Americans, they said.
Some members of the Biden administration supported the use of
booster doses even before the scientific advisers of the agencies had a chance
to review the data from Israel. Federal health officials intensified their
boosters-for-all campaign after the arrival of the omicron variant.
The CDC now recommends booster shots for everyone 12 and older,
five months after getting two doses of the mRNA vaccines made by
Pfizer-BioNTech and Moderna, or two months after a single dose of the Johnson
& Johnson vaccine.
The usefulness of booster shots in Americans younger than 50 was
a topic of vigorous debate in the fall. Several experts argued at the time that
third shots were unnecessary for younger adults because two doses of the
vaccine were holding up well.
Some of those experts remained unconvinced by the new data.
It was clear even months ago that older adults 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 a member of the FDA’s vaccine advisory committee.
But “where is 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 said. “We keep trying to further protect the already
protected.”
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
virus spread by preventing infections.
“They’re both data-driven, legitimate positions,” said John
Moore, a virus expert at Weill Cornell Medicine in New York. But at this point,
the debate is over: “We are using boosters in everyone and that’s what’s
happening.”
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