New data from scientists in Cambridge has revealed that there were more than 2,500 Omicron cases in the Anglia region last week.
The analysis by the Wellcome Sanger Institute suggests that the number of confirmed cases of the Omicron variant of coronavirus was three times higher than the previous week.
There were 2,625 cases in week to 18 December compared to 878 in the week to 11 December. That was an increase of 1,746 or nearly 200%.
The figures are estimates based on analysis of 60,000 test samples processed every week at the Sanger Institute labs.
Brentwood in Essex, where one of the first two cases of Omicron in the UK was identified, has the highest incidence rate with 114 cases per 100,000 in the population. It is also high in the neighbouring areas of Chelmsford, Epping Forest and Broxbourne in Hertfordshire.
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The Sanger Institute at Hinxton near Cambridge is contracted by the UK Health Security Agency to sequence coronavirus genomes so they can identify and track new variants of the virus.
It takes additional time to analyse and process the positive tests so there is a time lag in the publication of these figures compared with the daily data issued on the government's coronavirus dashboard.
There was a record daily number of confirmed coronavirus cases in the Anglia region on Monday 20 December with nearly 14,000 positive tests. That would have included all variants of the virus including Delta.
Watch an interview with Professor Ravi Gupta of the University of Cambridge
In separate research at the University of Cambridge, scientists are reporting that while Omicron may be significantly better than previous variants at evading vaccine-induced antibodies it is less likely to cause severe COVID-19 illness in the lungs.
The study was done by a team led by Professor Ravi Gupta at the Cambridge Institute of Therapeutic Immunology and Infectious Disease.
Prof Gupta said: "Omicron’s mutations present the virus with a double-edged sword: it’s got better at evading the immune system, but it might have lost some of its ability to cause severe disease."Prof Gupta told ITV News Anglia: "I don't think we're going to see the numbers of severely ill people that was projected. And that's good news, but we could still see quite a lot of activity and pressure on the NHS.
"We may have found ourselves in a more fortunate position this time than we expected but this does not prevent the next variant from regaining those qualities of Delta, for example, combined with a significant immune evasion and creating devastating conditions again.
"So we're not really there yet and we need to remain vigilant."
Find out more about the coronavirus data in the ITV Anglia region
The ITV Anglia region consists of the East of England counties of Bedfordshire, Cambridgeshire, Essex, Hertfordshire, Norfolk and Suffolk along with Milton Keynes, Rutland and Northamptonshire.