The U.S. Food and Drug Administration has authorized the use of a booster shot of Pfizer and BioNTech's COVID-19 vaccine for children aged 5 to 11, the regulator said on Tuesday.

The authorization makes everyone in the United States aged five and above eligible for booster doses of the vaccine, although the U.S. Centers for Disease Control and Prevention (CDC) still needs to sign off on the shots.

"While it has largely been the case that COVID-19 tends to be less severe in children than adults, the omicron wave has seen more kids getting sick with the disease and being hospitalized," FDA Commissioner Robert Califf said in a statement.

Califf said the authorization would help provide continued protection against COVID-19 in that age group. Data has shown that vaccine effectiveness starts to wane over time.

The U.S. government has been urging Americans to get boosters, and for the unvaccinated who are at much higher risk of severe COVID-19 and death to be inoculated.

But it is unclear how much many parents of children aged 5 to 11 will opt for a third dose. Just 28.8% of children in that age group are fully vaccinated, according to CDC data.

Children below the age of five are not yet eligible for a COVID-19 vaccine in the United States.

Roughly 66% of the U.S. population, or 220.6 million people, have received the full vaccination schedule so far, according to federal data. Of those, 102.3 million people have received one booster dose, and 11.7 million have received a second booster.

The CDC has scheduled a meeting of outside advisers to discuss vaccine boosters on Thursday. The agency's director has the final say on the administration of vaccines.