WASHINGTON DC — The US Tuesday
authorized a fourth dose of either the Pfizer-BioNTech or Moderna COVID-19
vaccines for people 50 and older, as authorities warn of a possible new wave
driven by the BA.2 variant.
اضافة اعلان
The
Food and Drug Administration (FDA) said in a statement it had based its decision on emerging evidence
that an additional booster, given four months after the last, improved
protection against severe COVID-19 and was not associated with new safety
concerns.
Additionally, people with immune
compromising conditions who have already received four shots, with their latest
at least four months ago, are now eligible for a fifth dose.
That includes people living with certain
organ transplants.
The Pfizer vaccine will be available to immune-compromised
people aged 12 and over, while the Moderna vaccine will be available to those
18 and up.
"Current evidence suggests some waning
of protection overtime against serious outcomes from
COVID-19 in older and
immunocompromised individuals," senior FDA scientist Peter Marks said,
explaining the decision.
The FDA said data from Israel, which had
studied the effects of a fourth dose given four months after the third on
700,000 people, found the extra shot was safe.
It also cited data from a study of 154
health workers whose antibody levels, including against the
Delta and
Omicron variants, were restored to high levels two weeks after their fourth doses.
A study published by Israeli researchers in
the New England Journal of Medicine this month indicated that three doses of
current generation mRNA vaccines have hit a ceiling in terms of the immune
response generated.
In other words, while three doses brings
immunity levels to new heights, the fourth dose restores antibody levels to
where they previously were shortly after the third.
Experts have said the benefits to younger,
healthy people are not yet clear, and say new vaccines will likely need to be
developed as the virus continues to mutate.
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