Pfizer filed with the Food and Drug Administration for authorization of its COVID-19 vaccine for young children on Tuesday.
The emergency authorization would include children who range in age from 6 months to 4 years old.
"This application is for authorization of the first two 3 µg doses of a planned three-dose primary series in this age group," the company said.
"Data on a third dose given at least 8 weeks after completion of the second dose are expected in the coming months and will be submitted to the FDA to support a potential expansion of this requested EUA," Pfizer added.
In mid-December, Pfizer reported that its vaccine did not produce an adequate response in children aged between 2 and 4. As a result, the company said children in that age group who were participating in the trial would need a third dose of the vaccine two months after their second shot.
The FDA will weigh a two-shot regimen of the Pfizer vaccine for young children, though the company will continue to research if a three-dose regimen produces a better immune response.
Pfizer's potential filing comes as the highly-contagious omicron variant continues to spread across the U.S., resulting in a sharp rise in infections among children.
Pfizer's vaccine is fully approved for people as young as 16 and is available through emergency use authorization for kids as young as 5.
The FDA issued full approval to Moderna's COVID-19 vaccine for people aged 18 and up on Monday.