WASHINGTON — Pfizer and BioNTech said on Thursday morning that they had asked federal regulators to authorize emergency use of their coronavirus vaccine for children ages 5 to 11, a move that could help protect more than 28 million people in the United States.

The companies have said they were submitting data supporting the change to the Food and Drug Administration. The agency has promised to move quickly on the request and has tentatively scheduled a meeting on Oct. 26 to consider it. A ruling is expected between Halloween and Thanksgiving.

Parents across the United States are anxiously awaiting the regulators’ decision, which could affect family life and the operation of schools. Clearance depends not only on the strength of the clinical trial data, but on whether they can prove to regulators that they are able to properly manufacture a new pediatric formulation.

Dr. Janet Woodcock, the acting F.D.A. commissioner, said last week that children might require “a different dosage or formulation from that used in an older pediatric population or adults.”

Pfizer has proposed giving children one-third of the adult dosage. That might require adding more diluent to each injection or using a different vial or syringe. The company was expected to describe the method it intended to use in its submission to the Food and Drug Administration.

Regulators will have to examine the purity and stability of mass-manufactured doses of the vaccine and determine that it matches the quality and potency of doses given to children in clinical trials. A pediatric dose will also most likely require new labeling, with special codes that would allow the Centers for Disease Control and Prevention to track specific lots in case of reports of serious side effects.

Children rarely become severely ill from Covid-19, but the Delta variant drove nearly 30,000 of them to hospitals in August. According to the American Academy of Pediatrics, nearly 5.9 million Americans younger than 18 have been infected with the coronavirus. Of the roughly 500 Americans under 18 who have died, about 125 were children ages 5 to 11.

“It really bothers me when people say kids don’t die of Covid,” said Dr. Grace Lee, an associate chief medical officer at Stanford Children’s Health who also leads a key advisory committee to the C.D.C. “They die of Covid. It’s heartbreaking.”

About one in every six Americans infected since the beginning of the pandemic was under 18 years old. But with the surge of the Delta variant, children accounted for as many as one in four infections last month, according to the American Academy of Pediatrics. The Food and Drug Administration authorized emergency use of Pfizer’s vaccine for 12- to 15-year-olds in May.

The infection rate in the United States is currently falling, prompting hope that the Delta variant is ebbing. But public health experts worry that the onset of colder weather could result in increased transmission.

Although federal regulators are under enormous pressure to quickly review Pfizer’s application, they also face other pressing decisions. Next week, they might rule on whether people who received the Moderna and Johnson & Johnson coronavirus vaccines should receive booster shots, both potentially contentious decisions.

Public health experts have said that the agency’s review of a Pfizer pediatric dose would be closely scrutinized. According to a recent survey conducted by the Kaiser Family Foundation, roughly a third of parents of children between ages 5 and 11 said they would wait and see before allowing their children to receive such a shot.

Dr. Walt A. Orenstein, an epidemiologist at Emory University and a former director of the U.S. immunization program, said that given the competing pressures on the Food and Drug Administration to make vaccine decisions quickly but carefully, public discussion was essential.

He said many parents were wavering between fear of Covid-19 and fear of side effects of a pediatric vaccine. If they were less worried about the consequences of coronavirus infection, he said, safety would be their top priority. If they were more worried, the vaccine’s effectiveness would matter more. As with other vaccines, Dr. Orenstein said, pediatricians would play a critical role in easing parental anxiety.