Boris Johnson is urging Britons to get their booster jabs in a Downing Street press conference, after new coronavirus restrictions were introduced to mitigate the impacts the new Omicron Covid-19 variant.
The prime minister wants to drive up Covid immunity as more and more cases of the Omicron variant emerge around the UK - experts are concerned about the coronavirus mutant as vaccines offer less protection against it.
Another eight cases of the new variant were found in England on Tuesday, bringing the UK total to at least 22.
Watch the briefing in full:
Mr Johnson is telling Britons the best way to ensure there is no lockdown at Christmas is to take up the offer of a booster jab, with third doses to soon be made available to all adults over 18, no sooner than three months after their first jab.
The PM is joined by Health Secretary Sajid Javid and NHS Chief Executive Amanda Pritchard.
It comes as England enters a new phase of coronavirus restrictions, with laws taking force today mandating that people wear masks in shops and on public transport, while new measures at the border mean any arrivals into the UK will be subject to more Covid-19 testing.
Anyone found not wearing a mask can once again face a £200 fine for a first time offence, with the amount going up the more people are found to break the rules.
The measures, which came into force at 4am, will be voted on retrospectively in the House of Commons this afternoon and despite some opposition from backbenches, the government is widely expected to win.
The booster jab programme was extended on Monday in another bid to tackle the Omicron variant, with over-18s now eligible for a third jab, three months after the second.
However, those under-40 with no underlying health conditions or who are not frontline health or social care workers cannot yet book their third jab.
On Monday, Health Secretary Sajid Javid said the NHS will be calling people forward "at the appropriate time".
The NHS will set out the "in next few days" how the new guidance will be "operationalised", Professor Jonathan Van-Tam, England's deputy chief medical officer, said as he announced recommendations at a Downing Street press conference on Monday.
Prime Minister Johnson defended England's new coronavirus rules ahead of Tuesday's press conference.
"The measures taking effect today are proportionate and responsible, and will buy us time in the face of this new (Omicron) variant," he said.
"Vaccines and boosters remain our best line of defence, so it is more important than ever that people come forward when eligible to get boosted."