U.S. regulators are urging drugmaker Pfizer to seek emergency approval for a two-dose regimen of its COVID -19 vaccine for children ages 6 months to 5 years while they wait for data on a three-dose regimen, with the goal of clearing the way for vaccinations as early as the end of February, a person familiar with the matter told The Associated Press on Monday.

The company’s application was to be filed as early as Tuesday.

Early data from Pfizer showed the vaccine – given to younger children at one-tenth the strength of the adult shot – was safe and produced an immune response. Last year, however, Pfizer announced that the two-dose vaccine had been shown to be less effective in preventing COVID -19 in children ages 2to 5. Regulators encouraged the company to expand the trial to include a third dose, believing that an additional dose would increase the vaccine’s effectiveness similar to a booster shot in adults.

Now, the Food and Drug Administration is urging the company to submit its application based on the data for the second dose for possible approval in February, and then return for additional approval once study data are available for the third dose, which is expected in March, according to the person familiar with the matter. The two-step approval process could mean young children could be vaccinated more than a month earlier than previously thought, assuming the FDA and Centers for Disease Control and Prevention give the green light to the vaccination.

The person spoke on condition of anonymity to discuss sensitive regulatory issues. The person said the lower effectiveness of the two-dose vaccine was not unexpected given the emergence of the highly transmissible Omicron variant of COVID -19. If young children could be vaccinated earlier with two doses, it would ultimately accelerate the time when they could receive the stronger protection expected with a third dose.

This would be welcome news for parents of young children, the last remaining age group without approval for COVID -19 vaccinations.

Young children are far less likely to get COVID -19 or die than adults, but cases in this age group have increased as cases of the Omicron variant have increased nationwide. Most cases and deaths occur in the elderly, especially in unvaccinated persons.

Accelerating the approval of pediatric vaccines against COVID -19 has been a priority of the Biden administration for more than a year, which it sees as critical to reopening and keeping schools and day care centers open – and helping parents who are busy caring for children return to work.

Vaccines for children ages 5to 12 were approved by U.S. officials in November, although uptake has been slower than U.S. officials had hoped.

Pfizer’s first series of vaccines will be administered three weeks apart. The third dose for young children is currently being studied for administration at least two months after the second dose.