Britain on Wednesday announced that it had ordered 60 million more doses of the Pfizer/BioNtech coronavirus vaccine for a booster programme aimed at protecting the most vulnerable during winter.

"The vaccine is helping us to bring back our freedom and we must protect this progress," Health Secretary Matt Hancock said at a news conference.

Faced with the "risk posed by a new variant", the government has been working on a programme to provide booster shots towards the end of the year, he added.

"We have been working on a programme of booster shots... for over a year now, and we've backed some of the only clinical trials in the world looking specifically at booster shots," he said. 

"I'm delighted to be able to tell you that we've secured a further 60 million doses of the Pfizer/BioNtech vaccine that will be used alongside others as part of our booster shot programme later this year."

Britain has been the European country worst-hit by the virus, recording more than 127,000 deaths, although it rolled out a succesful mass-vaccination campaign in early December, using AstraZeneca, Pfizer/BioNTech and Moderna vaccines. 

Nearly 34 million first doses have been administered, and a quarter of the adult population, or 13.5 million people, have received a second dose, according to official figures released Wednesday. 

The booster programme will be aimed at protecting the most vulnerable before winter.

The news came as a study by the Public Health Agency of England (PHE) showed that a single dose of Pfizer or AstraZeneca vaccine reduces the transmission of coronavirus within the same household by up to a 50 percent.