The Prime Minister will encourage people across the UK to get their booster jabs in his Christmas message this year, describing it as a 'wonderful' gift to their families.
Boris Johnson will also say that the pandemic is far from over, as 'Omicron is surging', and will pay tribute to the work of NHS staff.
Meanwhile, Labour leader Sir Keir Starmer thanked key workers who have 'saved countless lives' this year and paid tribute to the armed forces both home and abroad.
In his Christmas message released on Friday, Mr Johnson will say: 'Though the time for buying presents is theoretically running out, there is still a wonderful thing you can give your family and the whole country, and that is to get that jab, whether it is your first or second, or your booster.
'So that next year's festivities are even better than this year's.'
He will also describe a Covid vaccine as 'an invisible and invaluable present'.
The Prime Minister will add: 'We have been getting that vaccination that protects us and stops us infecting others.
'And I hope I can be forgiven for taking pride in the immense spirit of neighbourliness that the people of this country have shown.
'Getting jabbed not just for themselves, for ourselves, but for friends and family and everyone we meet.
'And that, after all, is the teaching of Jesus Christ, whose birth is at the heart of this enormous festival, that we should love our neighbours as we love ourselves.
'And so let's think of all those who are being good neighbours and thinking of others.
'All those in the NHS working over Christmas, our care workers, everyone involved in the incredible vaccination campaign.'
Earlier this week the Prime Minister confirmed no further Covid-19 restrictions will be put in place before Christmas.
However, the Government has said situation is finely balanced and remains difficult across the country, with the Omicron variant continuing to surge and cases at an all-time high.
The Government will continue to monitor the data closely and will not hesitate to act after Christmas if necessary.
As he opens his message, the Prime Minister will refer to the spread of Omicron, saying: 'After two years of this pandemic, I can't say that we are through it.
'How can I?
'When Omicron is surging, when we all know, we must together try to stop the spread of this new variant, we must test ourselves and take extra care when meeting elderly or vulnerable relatives.
'We know that things remain difficult.'
It comes as Sir Keir Starmer thanked key workers who have 'saved countless lives' this year in his Christmas message to the nation.
The Labour leader used his Christmas message to thank NHS staff for the vaccine rollout and also paid tribute to the work of the armed forces at home and abroad.
Sir Keir's statement came as daily Covid cases spiked again on Thursday, with hospitalisations rising by a fifth in a week, amid scientists' warnings that the UK is still in the 'danger zone'.
In his message, released last night, Sir Keir said: 'In the darkest of times, Christian values of kindness, of compassion and hope have shone through.
'Communities have come together to help one another. Key workers have saved countless lives.
'Armed service men and women both here and abroad have, as ever, played a huge part in protecting us all.
'Our brilliant NHS, which has done so much good since Labour founded it almost 75 years ago now, has vaccinated the country. You keep our country safe. On behalf of all of us, I want to say a heartfelt thank you.'
In the message Sir Keir also reflected on the 'unimaginable loss' experienced by many families this year, and that 'for too many, there will be one less chair at the table for the Christmas meal'.
But looking ahead to next year, he added: 'I believe that if we stick together, support each other and work together, we can find a path through.
'I know a better future is possible.'
In Scotland, Nicola Sturgeon has said the vaccination campaign had been 'a source of brightness during a really difficult month' as she used her Christmas message to urge Scots to get the jab.
In the First Minister's address on Christmas Eve she thanked all those who were working over the festive period, and paid special tribute to the thousands of people who had been involved in the race to vaccinate people ahead of the highly infection Omicron coronavirus variant.
'The vaccination programme has been a source of brightness during a really difficult month,' she said.
'Getting vaccinated is the most important way, although certainly not the only way, in which we can all protect each other, as we get through this next phase of the pandemic.
'Vaccination is above all else a demonstration of compassion for, and solidarity with, each other.
'By continuing to show compassion and solidarity, I hope we can all enjoy the best and the safest festive period possible.'
Wishing Scots a merry Christmas, Ms Sturgeon said for many December 25 would not be a holiday at all.
'That of course includes our armed forces, our emergency services, and so many other vital services,' said the First Minister.
'And of course for many people working in care homes, and in our National Health Service, Christmas will be another working day, at the end of another incredibly hard year. So thank you.
'I also want to say a special thank you to the thousands of people, who have been involved in the remarkable vaccination effort in recent weeks.
'I know that many of you are working right up until Christmas Eve, and will start up again straight after Boxing Day for the run up to new year.
'I know that, even three or four weeks ago, all of us were looking forward to a fairly normal Christmas. I am so sorry that this year's won't be quite like that.
'But for many of us, because of vaccination, it will still be more much normal than last year.'
Party leaders across the political spectrum have also wished fellow Scots a merry Christmas.