IE 11 is not supported. For an optimal experience visit our site on another browser.

FDA authorizes Covid vaccines for the youngest kids

The agency also authorized Moderna's vaccine for children ages 6 to 17.

The Food and Drug Administration on Friday authorized both Pfizer-BioNTech and Moderna's Covid-19 vaccines for young children, though the Centers for Disease Control and Prevention still needs to sign off before shots can be administered.

The Pfizer vaccine was authorized for children ages 6 months to 4 years, while the Moderna vaccine was authorized for children ages 6 months to 5 years, the FDA said in a statement. It also authorized Moderna's shot for kids ages 6 to 17.

Full coverage of the Covid-19 pandemic

The agency's authorization brings the roughly 18 million children under age 5 in the United States one step closer to getting vaccinated. Children in the age group are the only remaining group in the country ineligible to get the shots.

The FDA's decision will now go to the Centers for Disease Control and Prevention’s advisory committee, which will meet Friday and vote Saturday to decide how the vaccines should be used for children under 5. If all goes as planned, CDC Director Dr. Rochelle Walensky will sign off on the authorization, potentially within hours of the committee’s clearance. Shots in arms — or thighs for babies and most toddlers under age 3 — could begin as early as next week.

On Wednesday, the FDA's vaccine advisory committee unanimously recommended that the agency authorize both the Pfizer and Moderna vaccines for the nation's youngest children.

While many members of the committee noted that severe illness from Covid is less common in children than it is in adults, they said the shots should still be made available as an option for parents who wish to vaccinate their children.

Vaccination rates in children are still "too low," particularly in kids ages 5 to 11, FDA Commissioner Robert Califf said during a press briefing Friday. Less than 30 percent of children ages 5 to 11 have received two doses of a vaccine, according to CDC data.

Pfizer's vaccine regimen for little kids is two doses, given three weeks apart, followed by a third dose at least two months later. The shots are 3 micrograms each, one-tenth the dosage given to adults. Clinical trials found the shots to be 80% effective in preventing symptomatic Covid.

Moderna uses two 25 microgram doses, a quarter of the dosage given to adults. The shots are given four weeks apart. The shots were shown in clinical trials to be 40 to 50% effective at preventing milder infections, though the company has said it is testing a booster dose for the age group that could be distributed sometime this fall.

While the Pfizer and Moderna vaccines have different dosages and dosing schedules, both were shown in clinical trials to be safe and effective in young children, Dr. Peter Marks, the FDA’s top vaccine regulator, said during the Friday briefing.

He urged parents not to compare the vaccines, saying they should choose whatever shot is available to them. The differences between the vaccines are "relatively subtle," Marks said.

The most common side effects reported from the shots were pain at the injection site, irritability and drowsiness.

Follow NBC HEALTH on Twitter & Facebook.