The US Centers for Disease Control and Prevention has recommended COVID-19 vaccines for children as young as six months, allowing a rollout to start across the country next week.
The CDC's move came after a panel of advisers to the institution voted earlier on Saturday to recommend COVID-19 vaccines for children as young as six months.
"We know millions of parents and caregivers are eager to get their young children vaccinated, and with today's decision, they can," Rochelle Walensky, the CDC director, said in a statement.
The US Food and Drug Administration on Friday authorised Moderna Inc's shot for children aged six months to five years and Pfizer-BioNTech's vaccine for children aged six months to four years.
Pfizer's vaccine is already authorised for children over the age of five.
"This infection kills children and we have an opportunity to prevent that," Beth Bell, one of the doctors on the advisory panel, said following the vote.
"Here is an opportunity to prevent a known risk."
US President Joe Biden's administration plans to roll out the vaccines to the under-five age groups as early as next week.
"This coming week, parents will be able to start scheduling appointments at places like pediatricians' offices, children's hospitals and pharmacies," Biden said in a statement on Saturday.
"Appointments will ramp up as more doses are shipped out, and in the coming weeks, every parent who wants a vaccine will be able to get one. As the vaccination program ramps up, Vaccines.gov will be live next week with vaccine availability and appointments increasing throughout the week."
While some 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 five to 11 in October but only about 29 per cent of that group is so far fully vaccinated, federal data indicates.
CVS Health Corp plans to provide vaccines to children aged 18 months and older while Rite Aid Corp and Walmart Inc plan to offer these shots for kids who are at least three years old.
Infants are traditionally vaccinated at a doctor's office.
Public health officials have been pushing for childhood vaccinations ahead of the new school year as they hope shots for the age group will help prevent hospitalisations and deaths if COVID-19 cases rise again.
COVID-19 is generally more mild in children.
But the CDC says since March 2020 it has been the fifth-leading cause of deaths in children aged one-four and the fourth-leading cause of death in children younger than one.
The CDC advisers will meet again next week to consider whether to back use of the Moderna vaccine for children and adolescents aged six-17.
There has been some concern about the rate of rare cases of heart inflammation in teenage boys and young men from the Moderna vaccine and the advisers are expected to consider that data.