A new Moderna vaccine targeting two different variants of coronavirus will be used from September as part of the autumn booster campaign.
But how does this vaccine differ from others - and who is eligible for a booster?
Here's what you need to know.
What is the new Covid vaccine?
Moderna's new bivalent - or dual-strain - vaccine is the first to target two variants of Covid-19.
The company's chief executive officer Stephane Bancel described it as a “next generation" Covid vaccine and said it will play an “important role in protecting people in the UK" over the winter.
The UK became the first country in the world to authorise the vaccine when the Medicines and Healthcare products Regulatory Agency (MHRA) approved it on Monday, August 16.
How is it different to previous vaccines?
The dose is an updated version of the existing Moderna vaccine.
The new version - known as mRNA-1273.214 - contains the original Moderna vaccine, plus a modification targeted at the Omicron variant of coronavirus.
Bivalent vaccines have been developed since the emergence and dominance of the Omicron variant.
These vaccines contain two different antigens - substances that induce an immune response - based on two different strains of coronavirus.
The original vaccines contain one antigen, based on the original strain.
MHRA chief executive Dr June Raine said: "The first generation of Covid-19 vaccines being used in the UK continue to provide important protection against the disease and save lives.
"What this bivalent vaccine gives us is a sharpened tool in our armoury to help protect us against this disease as the virus continues to evolve."
Moderna's chief medical officer, Dr Paul Burton, previously said the new jab can boost a person's antibodies to such high levels that it may only be needed annually.
When will it be rolled out?
Care home residents and people who are housebound will be among the first to be vaccinated as the rollout begins from September 5.
A wider rollout is due to start on September 12.
Moderna's new vaccine has been approved for use as part of the programme, in line with guidance from the Joint Committee on Vaccination and Immunisation (JCVI).
NHS chief executive Amanda Pritchard said: “The NHS was the first healthcare system in the world to deliver a Covid-19 vaccine outside of clinical trials, and will now be the first to deliver the new, variant-busting vaccine when the rollout begins at the start of September.”
Who might be offered the new vaccine?
People will be offered the new vaccine "where appropriate and subject to sufficient supply", the NHS has said.
Based on advice from the JCVI, adults aged 50 years and over will be eligible for it during the autumn booster programme.
People aged 18-49 who meet the criteria for a booster can also be offered the new vaccine. This includes the clinically vulnerable, frontline health workers, unpaid carers or anyone living in a household with an immunosuppressed person.
However, not everyone who is called for a booster jab will be guaranteed the new vaccine. They may be offered the original Pfizer or Moderna vaccines, or a type known as Novavax in "exceptional" circumstances where no other suitable vaccine is available.
Current JCVI advice is that the bivalent Moderna jab is used for adults aged 18 years and above, who fall under the booster criteria.
Young people aged 12-17 who are eligible for a booster will be offered the Pfizer jab, and 5-11-year-olds will be offered Pfizer's paediatric formulation.
A JCVI spokesperson said that all of the available boosters provide good protection against severe illness from coronavirus.
Professor Wei Shen Lim, chair of Covid-19 immunisation on the JCVI, said: "It is important that everyone who is eligible takes up a booster this autumn, whichever vaccine is on offer.
"This will increase your protection against being severely ill from Covid-19 as we move into winter."
Up to 3,000 sites are expected to be part of the rollout, including GP practices and community pharmacies, and new venues may be added to the scheme.
How do I know if I'm eligible for an autumn booster jab?
Around 26 million people will be offered a booster jab this autumn.
Those who are eligible include:
All adults aged 50 and over
Residents and staff in care homes for older people
Frontline health and social care workers
Unpaid carers aged 16-49
People aged 5-49 who are clinically vulnerable (including pregnant)
People aged 5-49 who are household contacts of someone who is immunosuppressed
Several vaccines are approved for use as boosters, and not everyone will necessarily be offered the bivalent Moderna jab.
Who won't be called for a booster this autumn?
People aged 49 and below will not automatically be offered a booster unless they are:
Clinically vulnerable (including pregnant)
A frontline health or social care worker
A staff member in a care home for older people
An unpaid carer
A household contact of someone who is immunosuppressed
Who will get the vaccine first?
The priority is to vaccinate older care home residents and staff, and those who are housebound, followed by frontline health and social care workers.
People aged 50 or over, and the clinically vulnerable aged 5-49, are the next ones eligible.
Those living in the same house as an immunosuppressed person will then be called, followed by unpaid carers aged 16-49.
Can I have a Covid jab and flu jab at the same time?
Some people may be eligible for both the flu and the Covid booster vaccines.
If you are offered both vaccines it's safe to have them at the same time, and people are encouraged to take them up as soon as possible.
NHS director for vaccinations and screening Steve Russell said: “This winter will be the first time we see the real effects of both Covid and flu in full circulation as we go about life as normal – and so it is vital that those most susceptible to serious illness from these viruses come forward for the latest jab in order to protect themselves."
Does the new jab have any side effects?
The MHRA said that the vaccine's side effects are the same as those seen in the original Moderna booster dose and were typically mild.
Common side effects of the original Moderna vaccine are a sore arm, headache, nausea, tiredness and fever. They usually go away within a few days of appearing.
Will there be enough doses of the new vaccine available?
Vaccines minister Maggie Throup took to Twitter to reassure people about stock levels of the new vaccine.
She said: "We will have enough supply to offer everybody eligible new vaccines targeted at the Omicron variant."
It followed concerns that the country does not have enough doses to offer the new jab to all people eligible for the booster.
Officials would not confirm stock levels due to the commercial sensitivity of contracts.
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What if I am offered an original vaccine and not the new one?
The JCVI and the Medicines and Healthcare products Regulatory Agency (MHRA) have said the original vaccines continue to provide good protection and people should come forward regardless of the vaccine offered.
Professor Anthony Harnden, deputy chair of the JCVI, said people eligible for a Covid-19 booster jab should not worry about what type of vaccine they will receive.
"The key point is that people need to get vaccinated rather than worrying too much about the type of vaccine that they're receiving," he told BBC Breakfast.
"These are all very good vaccines, which have proven efficacy against severe disease - that's hospitalisation and death.
"The whole basis of the programme is to target those vulnerable people for a booster to keep their immunity topped up for protection against severe disease.
"So the message really is get vaccinated with your booster and don't worry too much about the type of vaccine that you're getting.
"But for simplicity's sake, we'll be trying to use one vaccine and we believe that this bivalent vaccine is potentially a very good vaccine and so we'll be using that in the first instance."
He said those eligible for the autumn booster programme "would not get second-rate vaccines", adding: "They're all very good vaccines.
"Both the Pfizer and Moderna original strain vaccines are available.
"There may well be other vaccines in the pipeline - Pfizer I believe are developing a bivalent vaccine which we'll look at very carefully on JCVI if it's approved.
"And of course, the government may order, or may have ordered, some more bivalent Moderna vaccines so that there's going to be a suite of vaccines which are available to use."