The Food and Drug Administration (FDA) on Friday authorised Moderna Inc's shot for children aged 6 months to 17 years old, and Pfizer-BioNTech's vaccine for children aged 6 months to 4 years of age.
The agency determined the known and potential benefits of both vaccines “outweigh” the known and potential risks for children.
Many parents and caregivers have been waiting for a vaccine for young children, FDA commissioner Robert Califf said.
White House Covid-19 Response Coordinator Dr Ashish Jha said the Biden Administration has been planning for authorisation for months.
“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,” he said.
“This is going to be a major milestone in the fight against the pandemic,” he said in a video posted to social media.
Within weeks, parents will be able to book vaccine appointments for their children, he said.
The White House said it has been planning to have the first vaccinations start as early as the week of June 20.
Ten million doses will be available initially and millions more in the coming weeks, it vowed.
The youngest age anyone can receive a vaccine in Britain is 5, according to the NHS.