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 Pfizer and German partner BioNTech SE said last week that they will
ask U.S. and European regulators within weeks to authorize a booster
dose due to an increased risk of infection after six months.
The companies did not share the data showing that risk, but said it
would soon be made public. A meeting with federal health officials
to discuss the matter was scheduled for Monday, Pfizer said.
In interviews with Reuters, some leading vaccine experts questioned
Pfizer's rationale and said that more data was needed to justify a
booster, especially as many countries struggle to administer the
initial vaccine doses needed to protect their citizens.
"It's disappointing that with such a complicated decision they took
such a unilateral approach," said Dr. Larry Corey, a virologist at
Seattle's Fred Hutchinson Cancer Center who is overseeing
U.S.-government backed COVID-19 vaccine trials.
The rise of the Delta variant, first detected in India and now the
dominant form of new coronavirus infections in many countries, has
raised concerns over whether currently available vaccines offer
enough protection. Several experts say a booster shot would be
warranted if there is a substantial increase in hospitalizations or
deaths among vaccinated people.
"That's the line for boosters," said Dr. Paul Offit, director of the
Vaccine Education Center at Children's Hospital of Philadelphia and
an advisor on vaccines to the U.S. Food and Drug Administration.
That has not been the case so far in the United States, where the
overwhelming majority of severe illness occurs in unvaccinated
people, he said.
Shortly after Pfizer's announcement late on Thursday, U.S. health
officials sought to reassure the public that anyone who already
received two doses of the drugmaker's vaccine was protected against
severe disease and death, even from the Delta variant.
"Americans who have been fully vaccinated do not need a booster shot
at this time," the FDA and Centers for Disease Control and
Prevention said in a statement.
A Pfizer spokesperson declined to comment on the criticism.
ISRAELI FINDINGS
Pfizer Chief Executive Albert Bourla and other officials have said
for months that they expect a regular booster shot will be needed
against COVID-19, a prospect that could help company profits for
years to come.
In explaining the decision to seek emergency authorization now,
Pfizer cited findings released last week by Israel's Health Ministry
suggesting the vaccine was only 64% effective at preventing
transmission and mild disease in the face of the Delta variant. The
ministry said it remains 93% effective at preventing
hospitalizations and death.
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 Pfizer's chief scientific
officer, Mikael Dolsten, told Reuters the
Israeli data showed that protection had waned in
individuals who got the vaccine in January or
February.
Pfizer board member Scott Gottlieb told CNBC
that those vaccinated included people who are
older and who had experienced asymptomatic or
mild COVID. "Frankly you do not
want them to get any infection because of the uncertainty of
infection in older individuals and how dangerous infection is in
older individuals," he said. "That's why I believe ... boosters will
likely be an option for older individuals who were vaccinated a
while ago heading into the fall and winter."
The Israeli Health Ministry, however, has not published any data
showing a specific correlation between infections among vaccinated
people and the date the vaccine was administered. On Sunday, the
government said it would offer a booster to adults with weak immune
systems who are at higher risk for severe COVID.
"I am not aware of valid clinical evidence coming from Israel that
establishes a higher risk of breakthrough infection, let alone
severe illness, associated with six months or more elapsing from
vaccination - not in a methodologically sound analysis suggesting
causal association beyond early descriptive hints," said Ran Balicer
of healthcare provider HMO Clalit and chair of the Israeli
government's expert advisory panel on COVID-19.
"I am not saying it could not be the case - but that to date I have
not seen such evidence," he said.
It is not clear at this point what might be causing the drop in
efficacy, Corey said. "Is it really due to waning antibody levels,
or is it something else?"
The U.S. government is backing two studies of a similar vaccine from
Moderna Inc that could shed more light on how the vaccines fare
against the Delta variant. Those results are expected in late fall.
Dr. William Schaffner, a vaccine expert at Vanderbilt University
Medical Center in Nashville, said he was encouraged by statements
from Pfizer that the company's own preliminary data show a third
vaccine dose produces a fresh spike in antibody levels, in case it
will be needed.
"But the argument for a booster right now, I don't find compelling,"
he said.
(Reporting by Julie Steenhuysen in Chicago and Michael Erman in New
Jersey; Additional reporting by Maayan Lubell in Jerusalem; Editing
by Michele Gershberg and Daniel Wallis)
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