Pfizer and BioNTech are delaying their Food and Drug Administration (FDA) request for the authorization of their Chinese coronavirus vaccine for children under the age of five, the company announced on Friday.

“Pfizer Inc. (NYSE: PFE) and BioNTech SE (Nasdaq: BNTX) today announced plans to extend their rolling submission to the U.S. Food and Drug Administration (FDA) seeking to amend the Emergency Use Authorization of the Pfizer-BioNTech COVID-19 Vaccine to include children six months through four years of age, which had been requested by FDA,” the February 11 press release reads, explaining that the trial for vaccines for young children is “ongoing.”

“Cases continue to accumulate according to the study protocol, and more data are being generated because rates of infection and illness remain high in children of this age, especially due to the recent Omicron surge,” the press release continued, attributing the delay to further data on the efficacy of a booster shot.

Emphasis added:

In December 2021, Pfizer and BioNTech announced that the ongoing clinical study would evaluate a third 3 µg dose at least two months after the second dose of the two-dose series in this age group. 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. This is also supported by recent observations of three dose booster data in several other age groups that seems to meaningfully augment neutralizing antibody levels and real world vaccine protection for omicron compared to the two-dose regimen. The companies expect to have three-dose protection data available in early April.

In November, the U.S. gave final approval to Pfizer’s coronavirus vaccine for children ages 5-11 as federal health officials continue to urge parents to get their children vaccinated. 

“I think people need to be assured that any decision that the FDA makes, as is historically always the case with them, will really be based on the scientific data of both safety and efficacy,” Fauci said of the trials for vaccines for young children. “And we can assure you that the decision will be based on that.”