The MHRA said the decision follows a “rigorous review” of safety and effectiveness in that age group.
Dr June Raine, MHRA chief executive, said: “We have carefully reviewed clinical trial data in children aged 12 to 15 years and have concluded that the Pfizer BioNTech Covid-19 vaccine is safe and effective in this age group and that the benefits of this vaccine outweigh any risk.
“We have in place a comprehensive safety surveillance strategy for monitoring the safety of all UK-approved Covid-19 vaccines and this surveillance will include the 12- to 15-year age group.
“No extension to an authorisation would be approved unless the expected standards of safety, quality and effectiveness have been met.
“It will now be for the Joint Committee on Vaccination and Immunisation (JCVI) to advise on whether this age group will be vaccinated as part of the deployment programme.”
More than 2,000 children were involved in the clinical trial to determine the safety of the Pfizer/BioNTech vaccine, the chairman of the Commission on Human Medicines said.
Professor Sir Munir Pirmohamed said: “We have been very careful to take into consideration the younger age group and the benefits of this population being vaccinated against any potential risk of side effects.
"There has been a thorough assessment and review of this data which was also looked at specifically by the CHM’s Paediatric Medicines Expert Advisory Group who are scientific experts within this age group, as well as the CHM’s Covid-19 Vaccines Benefit Risk Expert Working Group.
“We have concluded that based on the data we have seen on the quality, effectiveness and safety of the vaccine, its benefits do outweigh any risk.
"The MHRA will continue to scrutinise all of the suspected side effects data received through the rigorous surveillance programme in place through the Yellow Card scheme and other safety surveillance measures for all of the Covid-19 vaccines used in the UK.
“Over 2,000 children aged 12-15 years were studied as part of the randomised, placebo-controlled clinical trials. There were no cases of Covid-19 from seven days after the second dose in the vaccinated group, compared with 16 cases in the placebo group.”