Westminster has three cases of Omicron, while Barnet, Camden and Lewisham all have two cases within their boroughs.
And Bexley, Haringey, Newham, Sutton, Wandsworth all have one case.
Lambeth also has a case of Omicron - which was discovered in the most recent round of testing.
There are also 14 cases across the East Midlands, the East of England, the South East and the North West, making England’s total 29. There are additional cases in Scotland.
The individuals that have tested positive and their contacts are all isolating and work is underway to identify any links to travel to Southern Africa.
The UKHSA is carrying out targeted testing at locations where the positive cases were likely to be infectious.
Dr Jenny Harries, UKHSA chief executive, said: “We are continuing our efforts to understand the effect of this variant on transmissibility, severe disease, mortality, antibody response and vaccine efficacy.
“Vaccination is critical to help us bolster our defences against this new variant – please get your first, second, third or booster jab without delay.
“A booster dose for everyone over 18 years is now recommended and will be available at a minimum of three months from your last primary course jab.
“Please take up this offer as soon as you are eligible to protect yourself, your families and your communities.
“Please make sure to wear a mask in line with government guidance, including on public transport and in shops, to help break the chains of transmission and slow the spread of this new variant.
“It is very likely that we will find more cases over the coming days as we are seeing in other countries globally and as we increase case detection through focused contact tracing.
“That’s why it’s critical that anyone with Covid-19 symptoms isolates and gets a PCR test immediately.”
UKHSA has updated its stay at home guidance and non-household contacts guidance to reflect changes to self-isolation requirements for contacts of people who have been identified as a suspected or confirmed case of the Omicron variant of Covid-19.
Omicron Covid-19 cases in England:
- Barnet: 2
- Bexley: 1
- Brentwood: 1
- Buckinghamshire: 2
- Camden: 2
- Chiltern: 1
- Haringey: 1
- Lambeth: 1
- Lancaster: 1
- Lewisham: 2
- Liverpool: 1
- Newham: 1
- North Norfolk: 1
- Nottingham: 1
- Oxfordshire: 1
- South Cambridgeshire: 1
- South Northamptonshire: 2
- Spelthorne: 1
- Sutton: 1
- Three Rivers: 1
- Wandsworth: 1
- Westminster: 3
Is Omicron more transmissible?
There were early warnings that the variant could be more transmissible, given how quickly it had spread in South Africa’s Gauteng province - where up to 90% of new cases are already Omicron.
The reason why many scientists believe it can spread faster is that 10 of its 30 or so mutations are on the “spike” protein - the part of the coronavirus that acts a bit like a lock pick, changing shape to allow the virus to latch on to human cells.
However, the World Health Organization (WHO) has said that it is still too early to know for sure.
“It is not yet clear whether Omicron is more transmissible compared to other variants, including Delta,” they said.
“The number of people testing positive has risen in areas of South Africa affected by this variant, but epidemiologic studies are underway to understand if it is because of Omicron or other factors.”
Does Omicron cause more severe illness?
There are also conflicting reports on the severity of the disease caused by Omicron.
Dr Angelique Coetzee, the doctor who first spotted the new variant, said that patients have so far had “extremely mild symptoms” - although this may be due to a younger population.
The WHO also says “it is not yet clear” whether Omicron is any more severe, and that increasing hospitalisation rates in South Africa may be due to increasing case rates, rather than the variant itself.
Will the vaccines work against it?
The biggest question is whether Omicron can bypass immunity - whether that’s from the vaccine or previous infection.
Professor Jonathan Van-Tam said that the “number of mutations present, already on first principle, makes us worry about a possible effect on vaccine effectiveness” - although he was quick to stress that that there “are far more things we don’t know yet, than things we do know”.
Most scientists are expecting that we’ll have answers about vaccine efficacy against Omicron in two to three weeks - just before Christmas, in other words.
If a new vaccine is required, then all of the major pharmaceutical companies say they can develop tweaked vaccinations for Omicron.