Shielding advice will be different across the country and in each tier after the UK comes out of lockdown next week.
Speaking on Monday, Boris Johnson warned people to make a "careful judgement" over seeing their elderly and at-risk relatives over the Christmas period.
He also said that new guidance over shielding would be issued and how people should manage the risks in each tier.
The Prime Minister said: "I can't say that Christmas will be normal this year".
"In a period of adversity, time spend with loved ones is even more precious for people of all faiths and none.
"We all want some kind of Christmas, we need it, we certainly feel we deserve it.
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"But what we don't want to do is to throw caution to the winds and allow the virus to flare up again, forcing us all back into lockdown in January."
However, before people get too excited to see grandparents and elderly relatives, he went on to warn: "This virus is obviously not going to grant a Christmas truce, it doesn't know it's Christmas, and families will need to make a careful judgement about the risk of visiting elderly relatives."
Families will also need to keep in mind the risks of visiting relatives who are vulnerable to the virus, such as those on the clinically extremely vulnerable list who had previously been asked to shield.
He added: "We'll be publishing guidance for those who are clinically extremely vulnerable about how to manage the risks in each tier as well as over Christmas."
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As well as new tough tier restrictions, the mass roll-out of rapid lateral flow tests will also be key to suppressing the virus, according to the PM.
He said: "We're beginning to deploy these tests so people will once again be able to hug and hold hands with loved ones instead of waving at them through a window."
One specific example of where the testing could be used is in care homes.
Mr Johnson said that "by the end of the year" the roll-out of these tests will allow "every care home resident to have two visitors" who can be tested twice a week.