Covid cases have been rising in the UK in recent days, as well as the new Covid Omicron variant now being identified in various places across the nation.
The Government had been continuing with Covid Plan A in response to the number of coronavirus infections, but is set to implement its alternative plan for dealing with rising cases, known as Covid Plan B.
Here’s what you need to know.
What is Covid Plan A?
The Government originally set out plans to tackle Covid over the autumn and winter months in England with Plan A, which was set to be followed as long as the number of infections remained manageable and the NHS was not overwhelmed.
Plan A focused on continuing with the vaccine rollout, including offering it to healthy 12 to 15-year-olds, moving forward with the booster jab programme, and encouraging those who have not yet received any doses of the Covid vaccine to receive it.
The plan also encouraged people to get the flu jab, as well as frequent testing for Covid and self-isolation when required.
What is Covid Plan B?
Plan B will see the return of measures seen in the UK’s various lockdowns.
The Government has brought back guidance to work from home, alongside face masks in most indoor venues, including theatres and cinemas.
Exceptions to wearing masks include when eating, drinking, exercising or singing, Prime Minister Boris Johnson said.
Mandatory vaccine passports are being brought back for larger events and nightclubs, where people must prove they are double-jabbed.
Venues include those indoors that are unseated with more than 500 people, unseated outdoor venues with more than 4,000 people and any venue hosting more than 10,000 people.
A negative lateral flow test will also be sufficient proof, Mr Johnson said.
When will Plan B be introduced?
The measures will come into force over the next week, with people advised to work from home from Monday (13 December).
Face masks will be required from Friday 10 December, and vaccine passports will be introduced from Wednesday 15 December to allow businesses plenty of time to comply with the new rules.
Professor Neil Ferguson, from Imperial College London, whose data was instrumental to the UK going into lockdown in March 2020, said on Wednesday (8 December) that “case numbers of Omicron are doubling at least every three days, maybe even every two days at the moment, so it’s accelerating very fast”.
He said lockdowns are a possibility and cannot be ruled out, but working from home guidance could slow the spread.
“There is a rationale, just epidemiologically, to try and slow this down, to buy us more time principally to get boosters into people’s arms, because we do think people who are boosted will have the best level of protection possible, but also to buy us more time to really better characterise the threat,” he said.
He suggested “a kind of Plan B Plus with working from home might slow it down” rather than stopping Omicron, reversing the doubling time to every five or six days.
Although Prime Minister Boris Johnson has not confirmed a threshold for triggering Plan B, the plan describes "unsustainable pressure" on the NHS as the trigger.
Government scientific advisers are currently monitoring the number of Covid hospitalisations, any rapid or major changes in deaths or cases, and the overall state of the NHS.