The UK’s COVID alert level has been raised to its second highest following a rapid increase in cases of the Omicron variant.
The country’s four chief medical officers have recommended to ministers that the UK moves from level 3 to 4.
They warn Omicron is spreading much faster than Delta and there is less vaccine protection against symptomatic disease from the new variant.
They also said that people are already being treated in hospital due to Omicron and the number of patients is “likely to increase rapidly”.
And the medical officers urged the public to get their booster jabs if eligible as they “increase the immune response substantially and show good effectiveness”.
On Sunday, the UK reported 1,239 additional confirmed cases of Omicron – the highest daily rise and nearly double the previous high recorded on Saturday.
That takes the total numbers of cases of the variant to 3,137 in the UK.
The alert level upgrade means health authorities think rates of transmission are high and pressure is being placed on healthcare services.
It comes as Prime Minister Boris Johnson is set to give an address to the nation later this evening on the COVID vaccine booster programme.
The CMOs and NHS England’s Professor Stephen Powis said the emergence of Omicron “adds additional and rapidly increasing risk to the public and healthcare services”.
In a statement, they 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.”
They added: “Data on severity will become clearer over the coming weeks but hospitalisations from Omicron are already occurring and these are likely to increase rapidly.”
The medical officers say when vaccine protection is reduced – as is the case with Omicron – is it is “essential” that people top up with a booster jab.
They said both booster vaccines (Pfizer and Moderna) increase the immune response substantially and show good effectiveness although with some reduction compared to Delta.
On Friday, the UK Health Security Agency said two doses of the AstraZeneca and Pfizer/BioNtech vaccines offer little protection against the Omicron variant of COVID, but a booster raises their effectiveness to between 70 and 75 percent.
The UKHSA also said the country will have more than one million Omicron infections by the end of this month if current trends continue unchanged.
Analysis of 581 people with confirmed Omicron showed the AstraZeneca and Pfizer/BioNtech jabs provided “much lower levels of protection against symptomatic infection compared to the protection that they provide against Delta”, it said in a statement.
But it added: “The preliminary data showed effectiveness against the new variant appears to increase considerably in the early period after a booster dose, providing around 70-75% protection against symptomatic infection.”