Stormont ministers in Northern Ireland became the latest to unveil new measures to help combat rising case numbers of coronavirus, including the closure of nightclubs, and guidance to limit contacts with different households.
Here is how measures compare in the different UK nations.
What is the situation in England?
One big change which has taken place from December 22 is the rules surrounding the self-isolation period.
If a person in England has tested positive or has symptoms, they can stop self-isolating after seven days instead of 10 days if they receive two negative lateral flow test results on days six and seven.
Those who are unvaccinated close contacts of positive cases must still isolate for 10 days.
In terms of restrictions, Prime Minister Boris Johnson has reassured people that no further curbs will be introduced in England before December 25. He has yet to announce a post-Christmas Covid strategy for England.
England currently has the most relaxed rules in the UK, but a recent vote in Parliament saw some measures introduced, including Covid passes for entry into nightclubs and other venues as of December 15.
This applies to indoor events with 500 or more attendees where people are likely to stand or move around, such as music venues, outdoor events with 4,000 or more attendees, such as music festivals, and any events with 10,000 or more attendees, whether indoors or outdoors, such as sports stadiums.
Face coverings have also been made compulsory in most indoor public settings, as well as on public transport, and people have been told to work from home if they can.
People aged 18 and over are able to get their third jabs from this week.
England’s guidance is that people should work from home if they can. Anyone who cannot work from home should continue to go in to work – but is encouraged to consider taking lateral flow tests regularly.
What are the rules in Wales?
From December 26, groups of no more than six people will be allowed to meet in pubs, cinemas and restaurants in Wales.
Licensed premises will have to offer table service only, face masks will have to be worn and contact tracing details collected and the two-metre social distancing rules are set to return in public places and workplaces.
Sporting events will be played behind closed doors to help control the spread of the new Omicron variant.
Nightclubs will also be closed from Boxing Day under the new rules, although the Welsh Government has announced a £120 million fund to support any businesses affected by the restrictions.
Regulations will also be changed to include a requirement to work from home wherever possible.
A maximum of 30 people can attend indoor events and a maximum of 50 people at outdoor events. There will be an exception for team sports, where up to 50 spectators will be able to gather in addition to those taking part.
People attending weddings or civil partnership receptions or wakes are also being told to take a lateral flow test before attending.
What are the rules in Scotland?
From Boxing Day, large events will have one-metre social distancing and will be limited to 100 people standing indoors, 200 people sitting indoors and 500 people outdoors.
The following day, the one-metre physical distancing will be implemented between adults in all indoor hospitality and leisure settings, including pubs, bars, restaurants, cafes and other settings where food and drink is served, gyms, theatres, cinemas, bingo and snooker halls and bowling alleys.
Museums, galleries and other visitor attractions also have the same rules in place.
Table service is also required where alcohol is being served.
Ministers at Holyrood have announced a package totalling £375 million, including £175 million of additional funding from the Treasury, to support sectors affected by the latest protective measures to combat Omicron.
Since December 14, people have been asked to reduce their social contact as much as possible by meeting in groups of no more than three households.
Allowing staff to work from home where possible has become a legal duty on employers.
Care home visits have also been limited to two households.
What are the rules in Northern Ireland?
Northern Ireland deputy First Minister Michelle O’Neill said nightclubs will be closed from 6am on December 26.
Dancing will also be prohibited in hospitality venues, but this will not apply to weddings.
While nightclubs must close, other restrictions are coming into effect on the rest of the hospitality sector. People must remain seated for table service, while table numbers will be limited to six.
Ministers also agreed that sporting events can continue with no limits on capacity, while the work-from-home message is being bolstered and legislation introduced to require social distancing in offices and similar typed workplaces.
Weddings are exempted from the latest measures.
From December 27, the guidance is for mixing in a domestic setting to be limited to three households.