Britain crowed on Wednesday that Brexit had hastened its rollout of a Covid-19 vaccine while the EU lags on its own approval, provoking criticism that it was indulging in pharmaceutical nationalism.

The UK's Medicines and Healthcare products Regulatory Agency (MHRA), after giving its green light to introduce the Pfizer-BioNTech vaccine, gave a more nuanced view following the claims from Health Secretary Matt Hancock among others.

"Whilst until earlier this year we were in the European Medicines Agency (EMA), because of Brexit we've been able to make a decision to do this based on the UK regulator, a world-class regulator," Hancock told Times radio.

As a result, Britain was able to "not go at the pace of the Europeans, who are moving a little bit more slowly," he said.

Britain formally quit the European Union in January, and the EMA has relocated from London to Amsterdam.

But the country remains in a post-Brexit transition period until the end of this year, and EU pharmaceutical regulations still apply for now.

"We have been able to announce the supply of this vaccine using provisions under EU law which exists until January 1," MHRA chief executive June Raine told a news conference.

"Our speed and our provision has been totally dependent on the available data in our rolling review," she stressed, insisting the agency had taken no shortcuts in approving the vaccine.

The EMA on Tuesday said it would hold an extraordinary meeting on December 29 "at the latest" to consider its own emergency approval for the vaccine developed by Germany's BioNTech and US giant Pfizer.

Another US company, Moderna, said it was filing Monday for emergency authorisation of its vaccine in the United States and Europe.

Britain and the EU are meanwhile locked in tense negotiations to craft a new trading partnership from January 1.

Failure to strike a deal will seriously disrupt cross-Channel trade, although Hancock says planes are on standby to replace ships for ferrying supplies of the Pfizer-BioNTech vaccine to Britain from its manufacturing base in Belgium.

Business Secretary Alok Sharma noted that Britain was the first country to sign a deal with Pfizer/BioNTech, and "now we will be the first to deploy their vaccine".

"In years to come, we will remember this moment as the day the UK led humanity's charge against this disease," he said on Twitter.

That prompted a critical retweet from Germany's ambassador in London, Andreas Michaelis.

"Why is it so difficult to recognise this important step forward as a great international effort and success. I really don't think this is a national story," the envoy said.

"In spite of the German company BioNTech having made a crucial contribution, this is European and transatlantic."