A panel of experts convened by the US Food and Drug Administration recommended the Covid-19 vaccines by Moderna and Pfizer-BioNTech on Wednesday for the nation's youngest children.
Formal authorisations should follow quickly, with the first shots expected by next week after expected approvals by the Centres for Disease Control and Prevention.
“This recommendation does fill a significant unmet need for a really ignored younger population,” said Michael Nelson, a professor of medicine at the University of Virginia.
Prof Nelson was one of the 21 experts who unanimously said the benefits of the Moderna vaccine outweighed the risks.
Opening the meeting, senior FDA scientist Dr Peter Marks said that despite studies showing most children had now been infected with coronavirus, the high rate of hospital admissions among infants, toddlers and young children during last winter's Omicron wave showed the urgent need for vaccination.
“We are dealing with an issue where we have to be careful we don't become numb to the paediatric deaths because of the overwhelming number of older deaths,” Dr Marks said.
The US has recorded 480 Covid-19 deaths in the 0-4 age group so far in the pandemic, official data shows, far higher than even a “terrible flu season”, he said.
As of May, there had been 45,000 hospital admissions in that age group, nearly a quarter of whom required intensive care.
Both vaccines were tested in trials of thousands of children. They were found to bring on similar levels of mild side effects as in older age groups and caused similar levels of antibodies.
Efficacy against infection was higher for Pfizer, with the company placing it at 80 per cent, compared to Moderna's estimates of 51 per cent for children aged six months to 2 years and 37 per cent for those aged between 2 and 5.
But the Pfizer figure is based on very few cases and is thus considered preliminary.
It also takes three doses to achieve its protection, with the third shot given eight weeks after the second, and 11 weeks after the first.
Moderna's vaccine should provide strong protection against severe disease after two doses, given four weeks apart, and the company is studying a booster that would raise efficacy levels against mild disease.
But Moderna's decision to go with a higher dose is associated with higher levels of fever in reaction to the vaccine compared to Pfizer.
White House officials last week said the distribution of 10 million shots to pharmacies and doctors' offices could begin as soon as June 21.
