Omicron is very serious threat, what we know is bad - UK health official

Chief Medical Officer for England Chris Whitty attends a news conference on the coronavirus disease at 10 Downing Street, in London, Britain. [Reuters]

England's Chief Medical Officer Chris Whitty said on Wednesday that the Omicron coronavirus variant posed a really serious threat and that what health officials already knew about was "bad".

"This is a really serious threat at the moment. The how big a threat - there are several things we don't know, but all the things that we do know, are bad," Whitty told a news conference.

"And the principle one being the speed at which this is moving, it is moving at an absolutely phenomenal pace."

He added: "We do have some things going for us this time of which the most important is the existence of effective vaccines and the ability to boost at speed at this stage."