Millions of Brits are now eligible for a fourth dose of the life-saving coronavirus vaccine.
The Government has announced that certain sections of the population will be able to sign up for a second booster from this week.
The move comes almost exactly two years on from the first coronavirus lockdown in the UK, and against a worsening domestic pandemic picture.
A new, more infectious strain is spreading and case rates are up.
On Saturday Boris Johnson teased the latest vaccine drive at the Conservative Party's Spring conference - and hinted it'll be extended to more people later on this year.
He said: "I hope you've all had your boosters. We're getting ready for a fourth jab, because we're going to need it."
And Health Secretary Sajid Javid today said there will be more boosters “probably for those who are 50 or over” later this year.
Here is everything you need to know about the fourth jab:
When does the rollout begin?
As of today the NHS has started inviting eligible people to come forward for their life-saving Spring booster jabs.
Those who fit the bill have been able to to book from 7am.
Who is eligible now?
The Joint Committee on Vaccination and Immunisation has advised a spring jab should be offered to those most vulnerable to Covid-19 as a precautionary measure.
People aged 75 and over and those who are immunosuppressed over the age of 12.
In total five million people will be able to get a jab during the Spring booster campaign.
The NHS will be contacting over 600,000 people to invite them to book their vaccine this week.
You become eligible when you hit six months since your last booster, which is why not everyone is available straight away.
For most of them it will be the fourth dose, though for immunosuppressed people it might be the fifth.
Who might become eligible in future?
The Joint Committee on Vaccination and Immunisation (JCVI) is still debating whether to extend fourth doses more widely.
Last week Health Secretary Sajid Javid gave the strongest hint yet that there will definitely be a wider rollout.
But is understood no decisions have been made about who exactly would get the jab as part of this. I.e. whether to offer a fourth jab to all adults - or, instead, widen access but still keep it to certain groups such as the over-50s.
Today Mr Javid emphasised the JCVI "have said they're looking at an Autumn dose for over-50s," but with no decision yet.
Asked if the JCVI would say we needed more people jabbed, Mr Javid told ITV's Peston: "I think at some point they will.
"And they've actually been clear and their most recent advice is that they think that towards the end of this year, maybe in the autumn, there will be a need to give a lot more people a boost, an offer of a boost.
"But I'll wait for that advice."
Why is the government rolling this out now?
Coronavirus cases and hospitalisations are on the up, and experts fear that deaths could soon begin to rise as well.
Since the beginning of the month daily infections have more than doubled, from 30,000 cases a day on average per week, to 70,000 now.
At the moment case rates among the elderly are at a record high, with one in 29 people over 70 in England infected.
Although the vaccine has helped to keep the impact of those infections lower than in 2020 and the start of 2021, hospitalisation rates are now rising again.
There are currently about 1,900 Covid admissions a day across the UK - a 50% rise on this time a month ago.
The rise is being fuelled by more social interactions and BA.2, a new a mutation of the Omicron variant of coronavirus that accounts for the majority of new infections in the UK.
Nikki Kanani, GP and Deputy SRO for the NHS COVID Vaccination Programme, said: “Sadly, we are still seeing large numbers of people seriously unwell in hospital with Covid so it remains vital that those most at risk come forward when they are invited to do so.
“The response so far from the public to the largest and most successful vaccination programme in NHS history has been incredible, with more than nine in 10 people aged 75 and over getting their initial booster.
"The NHS Covid vaccination programme is once again ready to get people protected, so when you are invited please do come forward for your spring dose.”
How can I get the second booster?
NHS health chiefs are expecting high uptake of spring boosters amongst people aged 75 and over after 4.5 million of them got their top up jab over autumn and winter, and have recruited additional call handlers for the 119 service to help people book their vaccine appointment.
Calls to book an appointment can be made to 119, which are free from mobiles and landlines.
Lines are open every day from 8am to 8pm, and 119 can provide support in 200 languages.
Local NHS teams will be contacting care homes in their patch as they have done previously to arrange for spring boosters for people who are eligible and have been invited.
Hundreds of sites including community pharmacies, vaccination centres and hospital hubs are offering spring boosters to those most vulnerable to coronavirus.
Booking can also be made on the NHS website.
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Is it important that I get the booster if I am eligible?
According to the government, it is still important for severely immunosuppressed people who have been advised to have a 3rd primary dose, for example those undergoing cancer treatment, to get this before getting a booster, for maximum protection from Covid-19.
While having three jab significantly decreases your chances of falling badly ill or dying from coronavirus, the impact of the vaccine wears off over time.
Having a booster jab helps to keep immunity levels as high as possible.
Health and Social Care Secretary Sajid Javid said: “Spring boosters will help top up the immunity of the elderly and the most vulnerable to ensure they are protected and will help us continue to live with this virus.
“Thanks to the NHS for rising to the challenge yet again to get people boosted. Please come forward as soon as you are contacted.”
Vaccines Minister Maggie Throup added: “We are absolutely determined to protect those most vulnerable to Covid.
“Please take up the offer of a spring booster as soon as you are contacted by the NHS – it will protect you and ensure we can continue to enjoy our freedoms.”
