FDA staff said in documents that data for Moderna's vaccine showed
that a booster does increase protective antibodies, but the
difference in antibody levels before and after the shot was not wide
enough, particularly in those whose levels had remained high.
The documents were released ahead of a meeting later this week of
the FDA's outside expert advisers to discuss booster doses of the
vaccine.
The FDA typically follows the advice of its experts, but is not
bound to do so. A panel of advisers to the U.S. Centers for Disease
Control and Prevention (CDC) will meet next week to discuss specific
recommendations on who can receive the boosters, if the FDA
authorizes them.
"There was boosting, sure. Was it enough boosting? Who knows?
There’s no standard amount of boosting that is known to be needed,
and nor is it clear how much boosting happened in the study,” John
Moore, a professor of microbiology and immunology at Weill Cornell
Medical College in New York, said in an email.
Moderna is seeking authorization for a 50-microgram booster dose,
half the strength of the original vaccine given in two shots about
four weeks apart.
The company has asked regulators to clear a third round of shots for
adults aged 65 and over, as well as for high-risk individuals,
similar to the authorization gained by rivals Pfizer Inc and German
partner BioNTech for their mRNA vaccine.
President Joe Biden's administration announced plans earlier this
year to roll out booster doses for most adults, but some FDA
scientists later said in an article in journal The Lancet that there
was not enough evidence to support boosters for all.
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Data on the need for boosters
has largely come from Israel, which rolled out
the additional shots of the Pfizer/BioNTech
vaccine to large swaths of its population, and
has provided details on the effectiveness of
that effort to U.S. advisers. No
similar real-world study populations exist for the Moderna or
Johnson & Johnson vaccines.
The evidence for Moderna's booster appears to have "a lot of holes,"
said Dr. Eric Topol, a professor of molecular medicine and director
of the Scripps Research Translational Institute in La Jolla,
California, noting that the data provided was limited and offers no
insight into how the boosters actually perform in people.
"That is fairly short of what Pfizer had from Israel, where they had
the full restoration of the vaccine effectiveness from the booster,"
Topol said.
The FDA's advisers will also consider booster doses for J&J's
single-dose vaccine on Friday. The FDA has not yet released its
briefing documents on those shots.
J&J has asked the FDA to authorize a booster at least two months
after the initial shot. It said data suggests high-risk adults
should receive boosters earlier, but that lower-risk individuals
could benefit from waiting at least six months for their second
shot.
(Reporting by Michael Erman in New Jersey, Julie Steenhuyen in
Chicago and Manas Mishra in Bengaluru; Editing by Arun Koyyur and
Bill Berkrot)
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