US President Joe Biden's administration has ordered millions of Covid-19 vaccines for children aged 5 and under in anticipation of a possible federal authorisation next week, the White House said on Thursday.
"Today, the Biden administration is announcing an operational plan that will ensure that vaccines ... are readily available for our youngest kids and that we continue the critical work of ensuring that all families know the benefits of getting their children vaccinated against Covid-19," the White House said.
The administration said an FDA authorisation for Covid-19 vaccinations for the age group would be a "historic milestone" in the nation's effort to fight the virus.
Ten million doses have been made available for pre-order and the administration will "immediately" ship them if the FDA authorises a vaccine. Half of those doses will be Pfizer and the other half Moderna, a senior administration official said.
As of this week, about 1.45 million of the 2.5 million available doses of Pfizer have been ordered and about 850,000 of available Moderna shots have been ordered, officials said. More orders are expected in the coming days.
Children under the age of 5 are the last group of Americans who have not yet been recommended to receive Covid-19 vaccinations. About 20 million young children would become eligible for vaccination if the government authorises one or both shots.
The White House said 85 per cent of eligible children would be within eight kilometres of a potential vaccination site.
But it is not known how popular the shots will be: a recent survey suggests only 1 in 5 parents of young children would vaccinate their children right away.
Public health officials have been disappointed over how many older US children, who have been eligible for shots for months, have yet to be vaccinated - less than one third of children aged ages 5 to 11 have received the two recommended doses, government figures show.
Pfizer has asked the FDA to authorise three doses of its Covid-19 vaccines for children ages 6 months to 4 years. Each dose is one tenth of the amount adults receive.
Moderna has asked the FDA to authorise two shots for children aged six months to 5 years, each containing a quarter of the dose given to adults.
Vaccinations could begin in earnest as early as June 21, White House Covid-19 co-ordinator Ashish Jha told reporters last week.
The Associated Press contributed to this report