The US Food and Drug Administration on Friday authorised two COVID-19 vaccines for children aged 5 and under, opening the door to vaccinating millions of the country's youngest children.
The agency authorised Pfizer-BioNTech's vaccine for children aged 6 months to 4 years and Moderna's shot for those 6 months to 17 years.
Pfizer's is already authorised for those over the age of 5.
While many parents in the United States are eager to vaccinate their children, it is unclear how strong demand will be for the shots.
The Pfizer-BioNTech vaccine was authorised for children aged 5 to 11 in October, but only about 29 per cent of that group is so far fully vaccinated, federal data shows.
The vaccines could be rolled out to the under-5 age groups as early as next week, White House officials have said, although the Centers for Disease Control and Prevention still needs to make its recommendations on how the shots should be administered before the vaccination campaign can begin in earnest.
A panel of outside advisers began meeting on Friday to consider a recommendation to the CDC on the shots for those under five years old and will vote on Saturday.
CVS Health Corp, Walmart and Rite Aid Corp plan to provide COVID-19 vaccinations to young children in the United States if they are authorised by authorities, the companies said on Thursday.
"Those trusted with the care of children can have confidence in the safety and effectiveness of these COVID-19 vaccines and can be assured that the agency was thorough in its evaluation of the data," FDA Commissioner Robert Califf said in a statement.
Public health officials and experts say that even though a large portion of small children were infected during the winter surge due to the Omicron variant of the coronavirus, natural immunity wanes over time and vaccinations should help prevent hospitalisations and deaths when cases rise again.
The CDC advisers will meet again next week to consider whether to back use of Moderna for older children, aged 6-17.
Moderna shares rose 1 per cent while Pfizer shares were down 1 per cent in morning trading.