A panel of outside advisers to the Food and Drug Administration met Tuesday to endorse authorizing the COVID-19 vaccine developed by Pfizer and BioNTech for children 5-11, a major step forward in vaccinating the full population.

The final vote was 17 members in favor, with one abstention.

If approved, the shots would be the first to be made available in the United States to children younger than 12 and make an additional 28 million Americans eligible for vaccination.

The Vaccines and Related Biological Products Advisory Committee’s vote is not binding, but will be weighed heavily when the FDA makes its decision.

Pfizer, the Centers for Disease Control and Prevention (CDC) and the FDA made presentations to the committee, whose members also heard public comments before debating and voting.

If authorized by the FDA, the CDC's vaccine advisory panel will meet next week to make additional recommendations on who should receive the shots, and then the agency would issue its final guidelines.

The question the panel considered: “Based on the totality of scientific evidence available, do the benefits of the Pfizer-BioNTech Covid-19 vaccine when administered as a 2-dose series (10 microgram each dose, 3 weeks apart) outweigh its risks for use in children 5-11 years of age?"

The FDA advisers are voting on whether they believe the benefits of granting the vaccine emergency use authorization outweigh the risks. 

An FDA review last week affirmed results from Pfizer showing the two-dose shot was nearly 91% effective at preventing symptomatic infection in 5- to 11-year-olds. Researchers calculated the figure based on 16 COVID-19 cases in youngsters given dummy shots versus three cases among vaccinated children. There were no severe illnesses reported among any of the youngsters, but the vaccinated ones had much milder symptoms than their unvaccinated counterparts.

Most of the study data was collected in the U.S. during August and September, when the delta variant had become the dominant COVID-19 strain.

The FDA review found no new or unexpected side effects. Those that did occur mostly consisted of sore arms, fever or achiness.

Dr. William Gruber, Pfizer’s senior vice president for vaccine clinical research and development, said the rate of side effects in kids 5 to 11 was no higher than in older age groups — and actually lower in terms of fever and chills.

“Across the other systemic event parameters, you can see that responses were comparable or less to those seen in 16-to 25-year-olds, representing a satisfactory reaction profile,” he said.

Children are at a lower risk than adults of developing severe COVID-19, but Dr. Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, said children 5 to 11 are “far from being spared from this harm of COVID-19.”

He said there have been 1.9 million COVID-19 infections in that age group, resulting in more than 8,300 hospitalizations — about a third of which still require intensive care — and nearly 100 deaths.

The virus also has blamed for more than 2,500 cases of multisystem inflammatory syndrome, which causes inflammation of the heart, lungs, kidneys, brain, skin, eyes or gastrointestinal organs.

“In addition, infections have caused many school closures and disrupted the education and socialization of children,” Marks said.

Added Gruber in his presentation, “The need for a safe and effective vaccine for children 5 to less than 12 years of age is clear.”

Dr. Fiona Havers, a medical officer with the CDC, said studies have been mixed about whether infection rates differ for younger children compared to adults and adolescents, but she stressed, “What is clear is secondary transmission from children both to other children and to adults can and does occur.”

She said some children — 7-8% of those infected — were still experiencing COVID symptoms at leats three months after being diagnosed. The symptoms include in fatigue, headache, insomnia, trouble concentrating, muscle and joint pain, coughing.

“It's important also to consider the impact of post-COVID conditions and quality of life, which includes the limitations of physical activity, feeling distressed about symptoms, mental health challenges and decreased school attendance and participation,” she told committee members. 

In their review of Pfizer’s data, FDA scientists noted that the study wasn't large enough to detect extremely rare side effects, including myocarditis, a type of heart inflammation that occasionally occurs after the second dose.

But the FDA scientists concluded that in almost every scenario the vaccine's benefit for preventing hospitalizations and death from COVID-19 would outweigh any serious potential side effects in children. 

Committee member Dr. Cody Meissner of Tufts University School of Medicine said he thought the issue of myocarditis “is the principal concern that people have regarding use of these mRNA vaccines and in children.”

The CDC’s Dr. Matthew Oster said there have been 1,640 reports of myocarditis in people under 30 who received either the Pfizer or Moderna vaccines as of Oct. 6. Just 877 met the CDC’s case definition for myocarditis, and 637 cases are still under review. 

Of the 829 people who were hospitalized, 789 have been discharged, and 19 are still hospitalized — five in intensive care units, Oster said. The status of 21 people is unknown.

But COVID-19 also causes myocarditis. Oster said most of COVID-related cases appear to be due to multisystem inflammatory syndrome. 

The Pfizer children’s vaccine uses a lower dosage — a third of what is given to adults. Pfizer recommends the two shots be administered 21 days apart.

Dr. Nicholas Warne, Pfizer’s vice president of pharmaceutical research and development, told the committee the children’s vaccine will have different packaging — orange labels, caps and shipping cartons rather than purple — to prevent mix-ups leading to children receiving adult-size doses. 

“We've tried to maximize, as best we can, the number of ways we can differentiate the pediatric dosage form from the current dosage form,” Warne said. 

Pfizer’s vaccine is fully approved in the U.S. for people ages 18 and older, and it has emergency use authorization for 12- to 17-year-olds. 

The Biden administration said last week it has secured enough shots to vaccinate all kids 5 to 11. The shots could begin early next month, with some children fully vaccinated by Christmas, if regulators give their go-ahead.

The federal government is planning to make the vaccine available at tens of thousands of pharmacies, as well as doctors’ offices, children’s hospitals, community health centers, rural health clinics and some schools. 

The news came one day after drugmaker Moderna announced that its COVID-19 vaccine was safe and produced a robust immune response in children 6-11, and planned to submit that data to federal regulators soon for authorization.

The Associated Press contributed to this report.