With the emergence of the Omicron Covid variant, governments across the UK are pushing for people to receive a booster jab this winter.
But who is eligible for a booster jab of the Covid vaccine in England, Wales and Scotland?
And how can you book a booster jab in each country?
How to book a Covid booster jab in England
The NHS in England is working on plans to offer a booster dose to everyone aged 18 and over.
They also want to offer booster jabs to those 16 and 17-year-olds with a severely weakened immune system.
Booster doses will be offered three months after the previous does, though the timescale is currently six months.
Health secretary Sajid Javid said: "Our best weapon to fight the virus is to get as many jabs in arms as possible. That is why I asked the JCVI to urgently look at expanding and accelerating the vaccination programme in light of the Omicron variant.
"Thanks to their rapid advice we are now able to put our booster programme on steroids – and protect even more people even more quickly.
"We have set an ambitious target to offer booster jabs to all adults in England by the end of January, while ensuring those most vulnerable to the virus will continue to be prioritised for their booster, and having the gap between second doses and boosters."
Find out more about booking a booster jab in England here.
How to book a Covid booster jab in Wales
The Welsh Government have also followed the latest JCVI advice and are expanding the booster vaccination to all adults over the age of 18.
Booster jabs in Wales are being offered in order of descending age groups with priority given to the vaccination of older adults and those in Covid -at-risk groups.
Advice on the Welsh Government website says: "Please wait to be invited, your health board will contact you when it’s your turn.
"Booster vaccinations are being be offered in order of descending age groups, with priority given to the vaccination of older adults and those in a COVID-19 at-risk group.
"Health boards are working their way through those eligible, in order, as quickly and as safely as they can.
"Please do not contact your GP to ask about appointments."
More Welsh Government booster jab advice is available here.
How to book a Covid booster jab in Scotland
All adults in Scotland will be offered a booster vaccine as advised by the JCVI after results showed a third vaccine significantly improved protection against serious infection.
The booster jabs aim to curb a potential wave of infections caused by the Omicron variant.
So far, everyone aged 40 and over and people who are clinically vulnerable have been invited to book their booster jabs in Scotland.
But soon, everyone over the age of 18 will be able to book a booster jab.
These third doses will be offered no less than three months after the second dose of the vaccine was administered.
This time frame between second vaccine and booster jab has been cut from six months to three, as advised by the JCVI.
You can book your booster jab via the vaccine portal on the NHS Inform Scotland website.
Currently, people aged 40 and over can book their Covid vaccine via the NHS portal here.
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