A F.D.A. panel votes to recommend the Pfizer-BioNTech vaccine for those 5 to 11.

A key advisory committee to the Food and Drug Administration voted overwhelmingly to recommend the use of Pfizer-BioNTech’s coronavirus vaccine in 5- to 11-year-olds, bringing the vaccine a big step closer to about 28 million children. Shots could be offered as early as next week.

The panel endorsed giving the age group one-third of the dosage given to people 12 and older in two shots, three weeks apart. The committee’s recommendations on whether to authorize vaccines are not binding, but the F.D.A. typically follows them in the days after the vote.

That will turn the matter over to the C.D.C., which has its own expert panel scheduled to weigh in next week.

The F.D.A.’s outside experts voted after regulators argued that thousands of children between the ages of 5 and 11 have been hospitalized with Covid-19 and nearly 100 have died over the course of the pandemic. Seventeen committee members voted in favor of the pediatric dose; one abstained.

During a long debate beforehand, some committee members questioned whether every child in the age group really needed the vaccine or whether it should be limited to those at high risk of severe Covid-19.

Dr. Paul Offit, a panelist who heads the Vaccine Education Center at Children’s Hospital of Philadelphia, said it was “nerve wracking” to make public health decisions affecting millions of children based on studies involving just a few thousand participants.

But he said: “The question is when do you know enough? And I think we certainly know that there are many children between 5 and 11 years of age who are susceptible to this disease who could very well be sick and are hospitalized or die from it.”

Dr. Peter Marks, who heads the agency’s division that oversees vaccine approvals, told the committee Covid-19 is now one of the top ten causes of death among children 5 to 11. Nearly two million in that age group have been infected and 8,300 have been hospitalized, a third of whom have needed intensive care, he said.

Federal officials hope that the pediatric dose can help close a major gap in the U.S. vaccine campaign that has worried parents, educators and public health leaders. If the F.D.A. grants authorization, about 28 million children will become eligible. Only the youngest, children under 5, would remain uncovered.

Dr. Fiona Havers, a viral diseases specialist at the C.D.C., said that children aged 5 to 11 make up 10.6 percent of all cases but only 8.7 percent of the population. Children have higher levels than adults of the neutralizing antibodies that are essential for preventing infection, she said, but are at least as likely as adults to be infected, she said. She said there appear to be many more cases of infection than are publicly recorded.

Covid hospitalization rates in the 5 to 11 age group are three times as high for Black, Hispanic or Native American children as for white children, she said. More than 2,000 schools withover one million students were forced to close between early August and October because of outbreaks, she said.

The C.D.C. also presented blood test data indicating that 42 percent of young children had antibodies, sparking questions about whether many of them had been infected and developed natural immunity. Dr. Havers cautioned, however, that the children tested were already under clinical care and may not represent the general population.

“There’s clearly a lot of susceptible children still out there that are vulnerable to severe disease,” she said.

It is unclear how many parents would quickly vaccinate their elementary schoolers if given the chance. Polling has showed that roughly a third of these parents are eager to do so right away, while a third prefer to wait. Since federal regulators cleared Pfizer shots for children 12 to 15 in May, 46 percent of that age group has been fully vaccinated, compared with about 69 percent of adults.

Panelists were recently deluged by messages in an organized email campaign urging them to vote against recommending authorization, according to Dr. Offit.

Dr. Marks said he wanted to acknowledge the “strong feelings” for and against authorization, but stressed that the only question before the experts was whether to allow shots, not whether to mandate them.

But Dr. H. Cody Meissner, a panelist and the chief of the Division of Pediatric Infectious Diseases at Tufts Children’s Hospital, said he worried that authorization would quickly be followed by vaccine requirements for schoolchildren.

A. Oveta Fuller, an infectious disease expert at the University of Michigan, said “if I were a parent of a child in this age group, I would want to have the choice and they can’t have the choice unless the vaccine is available.” But she questioned whether the government would adequately track any adverse side effects.

Pfizer officials described safety data on two study cohorts of children ages 5 to 11, both of roughly equal size. The first group was followed for about two months, the second for about two and a half weeks. The company said the children tolerated the vaccine well, and no major safety concerns emerged.

Pfizer presented efficacy data only for the first group of about 2,200 children, saying its vaccine had an efficacy rate of 91 percent against symptomatic Covid-19.

F.D.A. scientists reviewed their own analysis that found the benefits of staving off Covid-19 with a pediatric dose generally outweighed the risks of the most worrisome side effects. Hong Yang, an F.D.A. scientist, said that even in a scenario where the risk of infection is low as it was in June, vaccination’s benefits may outweigh the risks of possible side effects. That’s because people hospitalized with Covid-19 tend to be sicker, and for longer, than those with certain heart conditions tied to the vaccine.

Federal health officials have said that cases of the heart conditions the F.D.A. considered — myocarditis, or inflammation of the heart muscle, and pericarditis, inflammation of the lining around the heart — after the second dose of a vaccine tend to be mild and resolve quickly. None of the children involved in Pfizer’s clinical trial developed those conditions, but that was expected given the small trial size and the rarity of those diseases.