A 'major incident' has been declared in London today (Saturday, December 18) as cases the Omicron variant of Covid-19 surge in the city.

London Mayor Sadiq Khan announced the decision on Saturday, which will see greater coordination between the emergency services in the capital and opens up the possibility of greater support from the government.

Speaking on the announcement, Khan said the rapid spread of Omicron, which studies have shown could better evade the immunity brought with two doses of a vaccine or previous exposure to the virus, was "hugely concerning".

"The surge in cases of the Omicron variant across our capital is hugely concerning, so we are once again declaring a major incident because of the threat of Covid-19 to our city," he said.

"The Omicron variant has quickly become dominant with cases increasing rapidly and the number of patients in our hospitals with Covid-19 on the rise again.

"We are already feeling the impact across the capital and while we are still learning about this variant, it’s right that London’s key agencies work closely together to minimise the impact on our city, including helping to protect the vital vaccination programme."

Khan continued to urge Londoners to take up the booster vaccine in particular, with studies showing that three doses of a Covid vaccine offered much improved protection against the Omicron variant.

"We know that the vaccine offers our best defence against the virus. There are now more clinics in London delivering vaccines than at any point during the pandemic. I urge all Londoners to book their appointment or to go to one of the many walk-in centres across the capital as soon as you can," Khan said.

The mayor previously declared a major incident on January 8 due to the rapid spread of Covid-19 and its impact on the NHS.

The news came as UK ministers were urged to consider a "circuit breaker" lockdown of new domestic restrictions in order to control the rapid spread of Omicron in the population.

Authorities were warned by scientific advisers that the spread of Omicron could increase hospitalisations to such an extent that the NHS could become overwhelmed with knock-on effects for many other areas of healthcare besides Covid.

Omicron is now the dominant coronavirus variant in London, with figures published by the UK Health Security Agency on Saturday showing that 83.4 per cent of a sample of detectable cases in the capital from December 15 and 16 were found to have S gene target failure (SGTF), a way of detecting the likely presence of Omicron.

The number of people in hospital with Covid-19 in London, which has seen some of the biggest rises in cases in the last seven days, has risen to 1,534, up 28.6 per cent on last week, according to Government figures on Friday.

A further 341 people with Covid were in hospital in London on December 17, rising from 1,193 on December 10.

Georgia Gould, chair of London Councils, said: "The rapid spread of Omicron across our city is of huge concern.

"Local councils have stepped up and played a vital role in supporting their communities through the pandemic, I know they will continue with these efforts but we cannot do this alone."

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