The new Covid variant may be associated with a “higher degree of mortality”, Boris Johnson has revealed.

The PM issued a warning about the variant, which was first identified in South East England, at a Downing Street briefing

He said: “We’ve been informed today that, in addition to spreading more quickly, it also now appears that there is some evidence that the new variant, the variant that was first identified in London and the south-east, may be associated with a higher degree of mortality.” 

The UK’s chief scientific adviser Sir Patrick Vallance said the coronavirus variant which emerged in Kent is “a common variant comprising a significant number of cases” and transmits up to 70% more easily than the original virus.

He said: “We think it transmits between 30% and 70% more easily than the old variant. We don’t yet understand why that is the case.

“It doesn’t have a difference in terms of age distribution … it can affect anybody at any age, similarly to the original virus.”

He added that among people who have tested positive for Covid-19, there is “evidence that there is an increased risk” of death for those who have the new variant compared with the old virus.

Vallance cautioned, however, that this is based on evidence which is “not yet strong” and there is “no real evidence of an increase in mortality” among those hospitalised by the variant.

“These data are currently uncertain and we don’t have a very good estimate of the precise nature or indeed whether it is an overall increase, but it looks like it is,” he added.

Vallance also said the new South African variant "doesn't have a transmission advantage over the UK variant".

Chris Whitty, England's chief medical officer, said the new UK variant is spreading throughout the world, especially in Israel.

Chief scientific adviser Sir Patrick Vallance revealed that with the original strain of Covid-19, roughly 10 out of every 1,000 men in their 60s who get infected would be expected to die.

With the new variant, this risk would rise to roughly 13 or 14 out of every 1,000.

Vallance however stressed that the data was "currently uncertain", but conceded "obviously this is a concern".

Johnson and Vallance stressed that current evidence suggests vaccines will work on the new variant, which transmits between 30% to 70% more easily.

The PM said: "All current evidence continues to show that both the vaccines we’re currently using remain effective both against the old variant and this new variant."

Johnson said it "depends on all of us" to avoid transmission of Covid and stay at home. 

The PM said there are more than 38,000 people in hospital, 78% higher than there were at peak of the first wave, and more than 4,600 people have been hospitalised in the last 24 hours.

He said the NHS is under significant strain and this is why the public must follow the rules.

But he added that 400,000 vaccinations have been carried out in the last 24 hours.

"There is more to do and the target remains stretchy," he says.

More to follow.