Strict rules forcing people identified as close contacts of Omicron cases to isolate for 10 days will be scrapped.
From Tuesday, fully jabbed people who come into contact with an infected person will instead be told to take daily lateral flow tests for seven days.
The new advice applies to all cases of Covid, regardless of whether it is the Omicron variant or other strains.
Unvaccinated adults must continue to self-isolate for 10 days if they are a contact of someone with Covid.
Boris Johnson announced tougher isolation rules for Omicron contacts last month following the emergence of the worrying new variant.
But Health Secretary Sajid Javid said today that these rules would be axed from Tuesday as the new variant is rapidly expected to be the dominant strain.
Ministers are keen to avoid a repeat of the "pingdemic" in the summer, where thousands of people were isolating due to contacts with Covid cases, leading to staff shortages in a number of sectors.
From Tuesday, fully vaccinated people will be told to take daily NHS lateral flow tests for seven days after being told they are a contact of a Covid case.
Those who test positive or develop symptoms must take a confirmatory PCR test and isolate until they get a result.
If the PCR result comes back negative, you can leave self-isolation but should continue to take rapid tests for the remainder of the seven days.
People are advised to limit their contact with other people outside their household, especially in crowded or enclosed spaces and with anyone who is more vulnerable.
You should also follow government guidance on wearing a mask and working from home where possible.
Mr Javid said: "The Omicron variant is quickly gaining ground in the UK and is expected to become the dominant strain by mid-December.
“We are taking this proportionate and more practical measure to limit the impact on people’s day to day lives while helping to reduce the spread of Omicron.
“Vaccines remain our best defence and I urge anyone yet to get a first and second jab to come forward and those eligible for a booster to get boosted as soon as possible.”
UKHSA boss Dr Jenny Harries said the new rules would limit the spread of the virus and urged people to get their booster jabs.
She said: "Our latest analysis shows that boosters provide the best protection against the Omicron variant, please go forward when you are called.
"If you haven’t had any vaccine, a first and second dose still gives you protection against becoming seriously unwell.
"Don’t worry about stepping forwards now – you will be warmly welcomed by our vaccination staff and I would strongly advise you to get vaccinated as soon as possible.”
People who cannot be vaccinated for clinical reasons are allowed to do daily testing, along with children aged 5 to 18-years-old.
Under 5s are exempt.
