British travellers who fail to take their booster coronavirus jabs will face renewed restrictions, it has been reported.
So far only 60 per cent of those eligible for their third jab have come forward for their booster vaccine.
Now it has been reported that there are plans being drawn up to reimpose quarantine and testing for those who have refused their third vaccine - even if they are double-jabbed.
Measures could be introduced to protect the UK against the spread of new coronavirus variants, it is reported.
Plans would change the definition of fully vaccinated from being double jabbed to being triple jabbed.
A Government source told The Mail on Sunday : "This is not going to happen immediately – but happen it will."
This comes as elderly and vulnerable have been urged to get their Covid booster jabs as part of a "national mission" to help avoid a return to coronavirus restrictions over Christmas.
So far almost 10 million people in the UK have received a top-up jab, but around 30 per cent of over-80s and 40 per cent of over-50s in England are yet to receive a booster shot of vaccine, the Department of Health and Social Care said.
Three million more people in England are being invited to have their coronavirus booster jabs next week.
People over 50 and those most at risk from Covid-19 are eligible for a booster six months after their second jab.
Health Secretary Sajid Javid said younger relatives should urge eligible parents and grandparents to take up the offer of a booster and the flu vaccine.
He said that if "we all come together and play our part" then the country can "avoid a return to restrictions and enjoy Christmas".
"Almost 10 million people in the UK have received their Covid-19 booster and third jabs, a phenomenal achievement in under two months," Mr Javid said.
"As we approach this milestone, I want to thank those who have come forward and urge everybody across the nation to get vaccinated, get protected and get boosted.
"We know immunity begins to wane after six months, especially for the elderly and the vulnerable, and booster vaccines will top-up their protection to keep people safe over the winter.
"I strongly urge everybody who is eligible for a Covid-19 booster or flu vaccine to take up the offer as soon as you can.
"For those not yet eligible, please help your parents, grandparents or vulnerable loved ones get their jabs, it could save their life.
"And if you haven't yet had your first and second vaccines, it is not too late, the NHS will always be there to welcome you with open arms.
"This truly is a national mission.
"If we all come together and play our part, we can get through this challenging winter, avoid a return to restrictions and enjoy Christmas."
NHS England will begin inviting those who had their second dose more than five months ago, meaning they can receive their top-up as soon as it has been six months since their last vaccine.
Government guidelines state that people who are 50 and over, or aged 16 and over with a health condition that puts them at high risk of contracting Covid-19, and had their second dose six months ago are eligible to get their booster.
NHS England said eight million people were vaccinated by Saturday out of 12 million people that have been invited.
By next week, 16 million invitations for a booster will have been sent since the NHS booster programme began.
Text invites will come from NHSvaccine and will include a link to the NHS website, enabling anyone eligible to book an appointment at a convenient site nearby.
People who have not received their invitation can book an appointment on the NHS website or call 119.
Eligible people can also attend local walk-in sites without an appointment and can find their nearest walk-in through the online site finder.
