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 The U.S. Food and Drug Administration (FDA) and the Centers for
Disease Control and Prevention (CDC) said, however, in a joint
statement that Americans who have been fully vaccinated do not need
a booster COVID-19 shot at this time.
Some scientists have also questioned the need for booster shots. The
European Medicines Agency did not immediately respond to a request
for comment. Pfizer's chief scientific officer, Mikael Dolsten, said
the recently reported dip in the vaccine's effectiveness in Israel
was mostly due to infections in people who had been vaccinated in
January or February. The country's health ministry said vaccine
effectiveness in preventing both infection and symptomatic disease
fell to 64% in June.
"The Pfizer vaccine is highly active against the Delta variant,"
Dolsten said in an interview. But after six months, he said, "there
likely is the risk of reinfection as antibodies, as predicted,
wane." Data would be submitted to the FDA within the next month, he
added.
Pfizer did not release the full set of Israeli data on Thursday, but
said it would be published soon.
"It's a small data set, but I think the trend is accurate: Six
months out, given that Delta is the most contagious variant we have
seen, it can cause infections and mild disease," Dolsten said.
The FDA and CDC, in their joint statement, said: "We are prepared
for booster doses if and when the science demonstrates that they are
needed."
Pfizer's own data from the United States showed an erosion of the
vaccine's efficacy to the mid-80s after six months, Dolsten said,
against the variants circulating there in the spring.
He stressed that data from Israel and Britain suggests that even
with waning antibody levels, the vaccine remains around 95%
effective against severe disease.
The vaccine, initially devised by Germany's BioNTech, showed 95%
efficacy in preventing symptomatic COVID-19 in a clinical trial the
companies ran last year.
PROMISING PROTECTION
Dolsten said early data from the company's own studies shows that a
third booster dose generates antibody levels that are
five-to-10-fold higher than after the second dose, suggesting that a
third dose will offer promising protection.
He said multiple countries in Europe and elsewhere have already
approached Pfizer to discuss booster doses, and some may begin
administering them before a potential U.S. authorization.
Dolsten said he believes booster shots are particularly important in
older age groups.
Dr. Eric Topol, a professor of molecular medicine and director of
the Scripps Research Translational Institute in La Jolla,
California, said basing the decision on waning antibody protection
ignores the role of important other parts of the immune response,
including memory B cells, which can make antibodies on demand when
challenged by the virus.
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 "You need better studies to be
able to assert that. It isn't just neutralizing
antibodies," Topol said. Pfizer
has previously said people will likely need a booster dose, though
some scientists have questioned when, or whether, boosters will be
needed.
BioNTech has previously argued that while antibodies are the body's
main weapon against an initial infection, the cellular immune
response mainly shields against the disease breaking out and
worsening.
Pfizer plans to launch soon a placebo-controlled efficacy trial of
the booster with 10,000 participants. The study will run throughout
the fall, Dolsten said, meaning it will not be completed ahead of
the company's filing with the FDA. Dr. William
Schaffner, a vaccine expert at Vanderbilt University Medical Center,
said even if Pfizer succeeds in getting its booster authorized by
the FDA, that would be only the first step. The booster would still
need to be reviewed and recommended by advisers to the CDC.
"It's not automatic by any means," he said. Schaffner said
realistically, most of the public health bandwidth in the United
States is still focused on encouraging Americans to get their first
and second doses of the vaccine.
Because boosters would drive increasing demand for vaccines while
much of the world is still unvaccinated, Dolsten said Pfizer is
looking at ways to increase production.
It is already targeting production of 3 billion doses this year and
4 billion shots next year. Dolsten declined to give a forecast of
exactly how many more doses the company could add.
Pfizer and BioNTech said they had designed a new version of the
vaccine targeting the Delta variant with a clinical trial likely to
begin in August, but added the current vaccine version had "the
potential" to protect against the variant.
Pfizer expects the COVID-19 vaccine to be a major revenue
contributor for years and has forecast sales of $26 billion from the
shot in 2021. BioNTech said in May that vaccine supply deals for
this year so far are worth 12.4 billion euros in revenues that
accrue to it, with more contracts on the cards.
Global spending on COVID-19 vaccines and booster shots could total
$157 billion through 2025, according to U.S. health data firm IQVIA
Holdings.
(Reporting by Michael Erman; Additional reporting by Julie
Steenhuysen in Chicago, Ludwig Burger in Frankfurt and Kanishka
Singh in Bengaluru; Editing by Dan Grebler, Leslie Adler and Emelia
Sithole-Matarise)
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