Pfizer and BioNTech on Tuesday asked federal health regulators to consider emergency use authorization for its two-dose COVID-19 vaccine regimen for children aged six months to five years old. 

The companies will continue to gather information on the need for a potential third shot in the age group, as was first reported by the Washington Post on Monday. 

“As hospitalizations of children under 5 due to COVID-19 have soared, our mutual goal with the FDA is to prepare for future variant surges and provide parents with an option to help protect their children from this virus,” Pfizer CEO Albert Bourla said in a release. “Ultimately, we believe that three doses of the vaccine will be needed for children 6 months through 4 years of age to achieve high levels of protection against current and potential future variants."

"If two doses are authorized, parents will have the opportunity to begin a COVID-19 vaccination series for their children while awaiting potential authorization of a third dose," he added.

“Our vaccine has already demonstrated a favorable safety, tolerability and efficacy profile in multiple clinical trials and real-world studies for all age groups starting from 5 years old,” Ugur Sahin, CEO and Co-founder of BioNTech, said. “If authorized, we are very excited about the prospect of offering parents the opportunity to help protect their children 6 months through 4 years of age from COVID-19 and the potentially severe consequences of infection.”

Early data has shown the vaccine — which is administered to younger kids at one-tenth the strength of the adult shot — is safe and produces an immune response. But last year Pfizer announced the two-dose shot proved to be less effective at preventing COVID-19 in kids ages 2-5, and regulators encouraged the company to add a third dose to the study on the belief that another dose would boost the vaccine’s effectiveness much like booster doses do in adults.

The company will likely return for additional authorization once it has the data from the third dose study, which is expected by March or April.

The nation’s 19 million children under 5 are the only group not yet eligible for vaccination against the coronavirus. Many parents have been pushing for an expansion of shots to toddlers and preschoolers, especially as the omicron wave sent record numbers of youngsters to the hospital.

If the FDA agrees, Pfizer shots containing just one-tenth of the dose given to adults could be dispensed to children as young as 6 months. Pfizer said Tuesday it had started submitting its data to the FDA and expects to complete the process in a few days.

A few steps remain before young children can start getting vaccinated: first, the FDA’s advisory panel must hear from Pfizer on the data submitted in Tuesday's request; should the 17-person panel approve the recommendation, the FDA – which is not required to follow the panel’s advisement – will take up the issue. 

Should the FDA approve the vaccine, an independent advisory panel for the Centers of Disease Control and Prevention would then take up the issue; CDC director Dr. Rochelle Walensky can choose to accept or deny the panel’s recommendation.

The FDA said Tuesday it will convene a panel of independent researchers and physicians in mid-February to help review the Pfizer data. 

Walensky gave the final clearance for kids 5-11 to receive doses of the Pfizer-BioNTech COVID-19 vaccine in early November, opening the door for around 28 million children to get vaccinated against the deadly virus. 

The Biden administration has been trying to speed the authorization of COVID-19 shots for children, contending vaccinations are critical for opening schools and day care centers and keeping them open, and for freeing up parents from child care duties so they can go back to work.

Yet vaccination rates have been lower among children than in other age groups. As of last week, just 20% of kids ages 5 to 11 and just over half of 12- to 17-year-olds were fully vaccinated, according to the American Academy of Pediatrics. Nearly three-quarters of adults are fully vaccinated.

While young children are far less likely than adults to get severely ill from the coronavirus, it can happen, and pediatric COVID-19 infections are higher than at any other point in the pandemic.

“What we’re seeing right now is still a lot of hospitalizations and unfortunately some deaths in this age group,” said Dr. Sean O’Leary of the University of Colorado, who is on the AAP’s infectious disease committee. If the FDA clears vaccinations for these youngsters, “that’s going to be really important because all of those hospitalizations and deaths essentially are preventable.”

For kids under 5, Pfizer’s study is giving participants two shots three weeks apart, followed by a third dose at least two months later. The company is testing whether the youngsters produce antibody levels similar to those known to protect teens and young adults.

In December, Pfizer announced that children under 2 looked to be protected but that the antibody response was too low in 2- to 4-year-olds. It’s not clear why, but one possibility is that the extra-low dose was a little too low for the preschoolers.

Since the preliminary results showed the shots were safe, Pfizer added a third dose to the testing in hopes of improving protection.

Given how well boosters are working for older age groups, “it makes some sense” that younger children could benefit from a third shot, O’Leary said. “I certainly can understand where both the company and the FDA are coming from in terms of wanting to move this along, anticipating that there’s going to be a third dose down the line.”

The Associated Press contributed to this report.