Early signs suggest the Omicron Covid variant is more transmissible than the current Delta strain, No. 10 has said. But the prime minister's official spokesman added it was still too early to draw conclusions - and any impact caused by Omicron would also depend on whether it caused severe illness.
There are currently 437 confirmed cases of Omicron in the UK, figures show. Earlier, Wales' health minister said they were expecting a significant wave of Omicron that would peak in January.
In Scotland, Covid rules are going to be reviewed daily as Omicron cases rise, and First Minister Nicola Sturgeon has urged employers to let staff work from home until at least the middle of January where possible. Scientists believe Omicron could spread more easily than Delta, and could out-compete Delta to become the dominant variant in the UK.
But much is still unknown, and it could still take weeks to understand how severe illness from the variant is and what it means for the effectiveness of vaccines. The variant is currently spreading in the community in multiple areas of England, Health Secretary Sajid Javid said.
The government's cabinet was given an update on the pandemic on Tuesday. Giving an account of the meeting afterwards, the PM's spokesman said: "The prime minister said it was too early to draw conclusions on the characteristics of Omicron but early indications were that it is more transmissible than Delta."
But he said that there was no hard agreement on the level of transmissibility, and it was "too early to tell" the effect on vaccine evasion or seriousness of the illness it would cause. The spokesperson also said that ministers did not discuss whether to introduce the government's ‘Plan B’ for winter - which could involve more restrictions if the pressure on the NHS becomes too much.