Health officials have declined to dismiss a report COVID-19 vaccinations could be given to children under 12 next year.
Coronavirus jabs are currently only licensed in the UK for children aged 12 and over.
But leaked proposals show health bosses are preparing to vaccinate children aged between five and 11 next spring, according to a report in The Sun newspaper.
The Medicines and Healthcare products Regulatory Agency (MHRA) has said "expected standards of safety, quality and effectiveness" must be met before jabs would be authorised for children in this age category.
A spokesperson said: "Extending the use of a COVID-19 vaccine to children aged five to 11 would only be authorised if the expected standards of safety, quality and effectiveness are met.
"As with children aged 12 and above, parents can be fully assured that for any potential authorisation in this age group, the safety of the children would be our top priority."
If the MHRA extended the licence for younger children, recommendations from the Joint Committee on Vaccines and Immunisation (JCVI) would be considered by the government before any rollout.
Responding to the newspaper report, a spokesperson for NHS England said: "The NHS regularly plans for how it would operationalise opening vaccines to more people so it is ready to extend the jab quickly when and if any decision is recommended by the JCVI."
An unnamed source quoted in The Sun said plans may change, but noted that asking parents for permission to vaccinate young children "is in the schedule".
In the US, health officials gave final approval to the Pfizer vaccine for use in five to 11-year-olds at the beginning of November, with doses to be administered at a third of the amount given to teenagers and adults.
Children aged 12 to 15 in the UK have been able to get a first vaccination since September, although the JCVI has not yet advised on second jabs for healthy 12 to 15-year-olds.
But in a recent update, experts advised that children aged 12 and over who have had a COVID infection should not get a vaccine until 12 weeks later.
Deferring could help to reduce even further the "very, very small" risk of heart inflammation after vaccination, experts from the UK Health Security Agency (UKHSA) have said.