The Government has launched a media blitz encouraging people to take up a Covid-19 booster jab, with thousands of bookings made this week already.
The push to encourage vaccine take-up comes as the daily number of cases reported in the UK surpassed 50,000 for the first time since mid-July.
Here are some questions about boosters answered.
Why is a booster vaccine needed?
A booster jab will top up the immunity of those already fully inoculated against the virus.
The NHS said a booster jab will help improve the protection you have from your first two doses of the vaccine, helping to give you longer-term protection against getting seriously ill from Covid-19.
Does a booster make a big difference?
A booster shot of the vaccine developed by Pfizer and BioNTech has a dramatic effect, the firms claimed after a trial. A booster dose given to patients who had the initial two jabs showed a relative vaccine efficacy of 95.6% when compared with those who did not receive a booster.
Pfizer said that during the study period, there were five cases of Covid-19 in the booster group, and 109 cases in the non-boosted group.
Who is eligible for the booster vaccine?
Those eligible for boosters include anyone aged 50 and over, people living and working in care homes for the elderly, and frontline health and social care workers.
All those who are clinically extremely vulnerable and anyone aged 16 to 65 in an at-risk group for Covid (who were included in priority groups one to nine during the initial vaccine rollout) will also be eligible for a jab. Adults who share a household with vulnerable people will also be offered the booster.
At what point do people receive a booster?
Booster doses can only be offered to people who are at least six months on from receiving their second dose of the coronavirus vaccine.
But there is talk of that changing?
Yes. The interval between a second dose of Covid-19 vaccine and a booster could be cut from six months to five under plans reportedly being discussed by ministers and experts.
The Government said the time interval between doses was a matter for the experts on the Joint Committee on Vaccination and Immunisation (JCVI).
What jab will be given as a booster?
The JCVI expressed a preference for people to get the Pfizer jab as a third dose, regardless of which jab they were initially given.
But it said that half doses of the Moderna jab could be used as an alternative.
Some people may be offered a booster dose of the Oxford/AstraZeneca vaccine if they cannot have the Pfizer/BioNTech or Moderna vaccine, the NHS said.
How do I book a booster appointment?
The NHS says most people will be invited to book an appointment at a larger vaccination centre, pharmacy, or local NHS service such as a GP surgery.
People who have not received an invitation within one week of the six-month milestone can book an appointment online without an invitation.
Can I get the flu jab at the same time as the booster?
Yes. The NHS says that most people who can get a Covid-19 booster vaccine are also eligible for the annual flu vaccine and it is safe to have them at the same time.
What has take-up been like?
An estimated 4.7 million booster doses of the Covid-19 vaccine have been delivered in the UK, up from Wednesday’s total of 4.4 million.
In what ways are people being encouraged to get the booster?
A television advert urging people to “get vaccinated, get boosted, get protected” will play from Friday evening, featuring an NHS nurse explaining the benefits of the flu jab and the coronavirus booster vaccine.
Targeted digital adverts will also feature on social media platforms, digital radio and video websites such as YouTube.