Boris Johnson will address the nation tonight in a televised broadcast on Covid as the UK's threat level was raised.
The Prime Minister will give a Covid update at 8pm from Downing Street, which is expected to focus on ramping up the booster rollout.
The UK Covid Alert Level increased from Level 3 to Level 4 earlier today "in light of the rapid increase in Omicron cases", the four UK chief medical officers said.
The joint statement said: "Transmission of COVID-19 is already high in the community, mainly still driven by Delta, but the emergence of Omicron adds additional and rapidly increasing risk to the public and healthcare services.
"Early evidence shows that Omicron is spreading much faster than Delta and that vaccine protection against symptomatic disease from Omicron is reduced.
"Data on severity will become clearer over the coming weeks but hospitalisations from Omicron are already occurring and these are likely to increase rapidly."
Mr Johnson is due to discuss a significant expansion of the booster programme as fears mount over the spread of Omicron.
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