Britain's government said on Saturday it had told England's health service to get ready for a mass Covid-19 vaccination programme for children aged between 12 and 15 starting in September, if vaccination experts give the green light.
A first vaccine dose has already been offered to all 16 and 17-year-olds in England as well as to 12 to 15-year-olds with specific underlying health conditions and those who live with someone who is immuno-suppressed.
Britain has so far not followed the example of many other countries which have pressed ahead with widespread vaccinations for children younger than 16.
Most children develop only mild or no symptoms from COVID-19, but they are able to spread the virus.
Britain's health ministry said "we need to be ready to hit the ground running and start those vaccinations as soon as possible" if the government's vaccination advisers backed extending the programme to all 12 to 15-year-olds.
The advisers are currently weighing up the possible harms and benefits of such an extension.
However, British health regulators have already said that the Pfizer/BioNTech and Moderna vaccines are safe and effective for those aged between 12 and 17.
England's health service will begin contracting providers to recruit and train staff to provide school-aged immunisations to ensure teams would be ready to start offering vaccinations in schools from early September, the health ministry said.
Parental or carer consent would be sought before giving children vaccinations, it said.
The devolved administrations in Scotland, Wales and Northern Ireland have their own powers over health policy. As in England, they are not currently offering Covid-19 vaccinations to all 12- to 15-year-olds.