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FDA Committee Delays Review of Pfizer-BioNTech’s COVID-19 Vaccine for Young Kids

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The U.S. Food and Drug Administration (FDA) postponed a meeting to discuss the authorization of Pfizer-BioNTech’s COVID-19 vaccine for children younger than five, again pushing back the timeline for vaccinating the youngest Americans.

The FDA’s Vaccines and Related Biological Products Advisory Committee was scheduled to meet on Feb. 15 to discuss emergency use authorization of a two-dose regimen of Pfizer-BioNTech’s vaccine formulated for children ages 6 months through 4 years. (Pfizer is testing a three-microgram dose for young kids, smaller than the doses offered to adults and older children.) But on Feb. 11, the FDA announced that Pfizer had notified the agency of new data from its ongoing clinical trial testing a three-dose regimen for kids, necessitating a longer review period.

“FDA and Pfizer want completed studies on the three-dose product before reviewing the data,” Dr. Paul Offit, director of Children’s Hospital of Philadelphia’s Vaccine Education Center and a member of the FDA’s vaccine advisory committee, wrote in an email to TIME.

The delay “will give the agency time to consider the additional data, allowing for a transparent public discussion as part of our usual scientific and regulatory processes for COVID-19 vaccines,” the FDA said in a statement.

The FDA did not announce a new date for the advisory committee meeting, but Pfizer and BioNTech said in a press release that they expect to have data on the three-dose vaccine schedule in early April. “Given that the study is advancing at a rapid pace, the companies will wait for the three-dose data as Pfizer and BioNTech continue to believe it may provide a higher level of protection in this age group,” the statement says.

Read More: The Childhood Vaccine Debate Ignores a Crucial Point: Kids Aren’t Supposed to Die

Pfizer’s rush to get its vaccine authorized for the youngest children faced a setback in December, when researchers announced that two doses of the pediatric vaccine did not spark a satisfactory immune response in children ages 2 to 4. At the same time, Pfizer announced that it had tweaked its study protocol to include a third dose, in hopes that it would provoke a stronger reaction.

Nonetheless, at the FDA’s request, Pfizer submitted data on the two-dose regimen in February so that the agency could begin its emergency use authorization process in light of Omicron’s continued threat to unvaccinated people.

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“Ultimately, we believe that three doses of the vaccine will be needed for children 6 months through 4 years of age to achieve high levels of protection against current and potential future variants,” Pfizer’s CEO Albert Bourla said in a statement at the time. “If two doses are authorized, parents will have the opportunity to begin a COVID-19 vaccination series for their children while awaiting potential authorization of a third dose.” Now, however, that review process has been paused in favor of waiting for more data.

It’s not clear what that additional data will mean for the shot’s authorization among the millions of children younger than 5 in the U.S. But parents—many of whom have been anxiously awaiting vaccines for their young children—are likely to be dismayed at the extra waiting time.

“I’m disappointed as a mom, but I’d rather that our regulators play it extra safe and wait for data from 3-doses rather than authorize 2-doses in the meantime,” Dr. Leana Wen, a professor at the George Washington University Milken Institute School of Public Health, wrote on Twitter.

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Write to Jamie Ducharme at jamie.ducharme@time.com