The addition of an extra dose came after a preliminary
analysis found 2- to 4-year-olds didn’t have as strong an immune response as
expected to special low-dose shots.
Pfizer had planned to release data from its study of
children under 5 by the end of the year. It’s not clear how this change will
delay the quest to vaccinate the youngest children.
Pfizer and its partner BioNTech said if the three-dose study
is successful, they plan to apply for emergency authorization sometime in the
first half of 2022.
A kid-sized version of Pfizer’s vaccine already is available
for 5- to 11-year-olds, one that’s a third of the dose given to everyone else
12 and older.
For children younger than 5, Pfizer is testing an even
smaller dose, just 3 micrograms or a tenth of the adult dose.
Researchers analyzed a subset of youngsters in the study a
month after their second dose to see if the tots developed levels of
virus-fighting antibodies that were similar to teens and young adults who get
the regular shots.
Youngsters under age 2 had similar antibody levels, but the
immune response in 2- to 4-year-olds was lower, Pfizer vaccine research chief
Kathrin Jansen said Friday in a call with investors.
So the study is being expanded to evaluate three of those
very low-dose shots in children under 5. That third shot will come at least two
months after the youngsters’ second dose.
No safety concerns have been spotted in the study, the
companies said.
Jansen cited other data showing a booster shot for people 16
and older restores strong protection, a jump in immunity that scientists hope
also will help fend off the new omicron variant.
The companies also are preparing to test a booster for 5- to
11-year-olds, who are just now getting their two-dose vaccinations. And they
are testing different dose options for teen boosters.
Jansen said if the additional pediatric testing is
successful, “we would have a consistent three-dose vaccine approach for all ages.” -AP
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