Boris Johnson will deliver a coronavirus press conference today after warning of the threat of a Covid "blizzard" from Europe.
The Prime Minister will be accompanied at the Downing Street briefing at 3pm by Chief Scientific Adviser Sir Patrick Vallance and Chief Medical Officer Professor Chris Whitty.
Mr Johnson is expected to address changes to the booster rollout after the vaccine experts recommended extending it to people aged 40 to 49-years-old.
Ministers across the UK have accepted the advice from the Joint Committee on Vaccination and Immunisation (JCVI) with invites going out as soon as possible, Health Secretary Sajid Javid confirmed.
The PM warned that the risk of a "blizzard" of coronavirus cases coming from Europe could derail Christmas unless people got their booster jabs.
The European Centre for Disease Prevention and Control's most recent overview listed 10 countries as being "of very high concern" - Belgium, Bulgaria, Croatia, Czech Republic, Estonia, Greece, Hungary, the Netherlands, Poland and Slovenia.
It said there was "high and rapidly increasing overall case notification" across the EU.
Infection rates in the UK are still around the levels of the peak of the second wave in January but death rates are significantly lower.
Speaking on a visit to a vaccination centre in London, Mr Johnson said: "We don't see anything in the data at the moment to suggest that we need to go to Plan B, we're sticking with Plan A.
"But what we have certainly got to recognise is there is a storm of infection out there in parts of Europe, you can see those numbers ticking up very sharply in some of our continental friends.
"And we've just got to recognise that there is always a risk that a blizzard could come from the east again, as the months get colder.
"The best protection for our country is for everybody to go forward and get their booster."
The PM has resisted calls to impose further Covid restrictions in England in recent weeks as the Government continues to focus on vaccination as the way out of the pandemic.
With the winter months approaching, Mr Johnson warned people to get their booster jabs to ensure Christmas can go ahead.
He said: "If you can get your booster then your immunity goes right back up to 95%. So far we've got 75% of everybody over 70 getting a booster, there's a huge number of people, but it's that further 25% that will make all the difference to winter, to Christmas, to our plans going forward, because it's that extra level of protection that we really need."
Earlier, Tory chairman Oliver Dowden did not rule out imposing tougher restrictions - saying: "It is in our hands. If you get the booster when the call comes that is the biggest wall of defence that we have against Covid."
Asked if the Government would repeat its mistake of being too slow to shut borders, he said: "Of course we keep these things under review all the time. We have move moved away from some of those restrictions.
"We haven't ruled it out and of course if the situation changes dramatically we would have to review that again."
