LONDON, Dec 15 (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. Chief Medical Officer for England Chris Whitty attends a news conference on the coronavirus disease (COVID-19) at 10 Downing Street, in London, Britain November 15, 2021. Leon Neal/Pool via REUTERS Chief Medical Officer for England Chris Whitty attends a news conference on the coronavirus disease (COVID-19) at 10 Downing Street, in London, Britain November 15, 2021. Leon Neal/Pool via REUTERS "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."