The new Omicron variant of Covid-19 is spreading across the UK fast – and it has prompted Boris Johnson to bring in “Plan B” restrictions to curb the spread.

It means members of the public are being urged to get their third vaccine jab to boost immunity as soon as they can.

While it was hoped that the booster alone would be enough to fend off the virus this winter, the emergence of the new strain, thought to be more transmissible than the Delta variant, has forced the government’s hand in rolling out new protective measures.

Face masks are once again mandatory on public transport, in shops, cinemas, theatres and places of worship in England.

Meanwhile, employees are being advised to work from home where possible and an NHS Covid Pass is now required for entry to crowded venues.

NHS rules on boosters have also been relaxed so that all over-18s are now being offered their third jab, a decision supported by the Joint Committee on Vaccination and Immunisation, which also recently recommended cutting the period between second and third jabs from six months to three in a bid to beat the variant.

But the UK has nevertheless continued to experience extremely high levels of Covid infections across the festive period, with total daily cases in England rocketing to a pandemic high of 218,724 on 4 January, according to the UK Health Security Agency.

Fortunately, the rates of hospitalisations and deaths remain relatively low, although no fewer than 24 NHS trusts have reported “critical incidents” of staff shortages, placing remaining staff under huge pressure.

All of which means a third “top-up” vaccine is becoming even more necessary as immunity begins to wane.

You can currently get a booster if you are over 18 - or over 16 with a health condition - and it has been at least three months (91 days) since you received your second dose of one of the approved Covid vaccines.

If you are eligible for a vaccine booster jab, you no longer have to wait for the NHS to contact you to make an appointment online.

If you are struggling to secure a booking due to high demand, you can also visit any walk-in vaccination centre to get your jab, with people being advised to use the NHS online walk-in finder to locate their nearest centre.

If you have had a positive Covid test, you are advised to wait four weeks (28 days) before booking your booster, starting from the date you had the test.

“NHS staff are making it as easy as possible for people to get their top-up vaccination,” said Dr Nikki Kanani, deputy lead for the NHS Covid-19 vaccination programme.

“People can now go online, find their nearest site and go and get their booster without delay.

“The booster is not just nice to have, it is really important protection ahead of what we know will be a challenging winter.

“So if you are eligible, please do check the site finder and go get your jab.”

This article was amended on 10 December 2021. It had previously stated that Covid boosters were available to everybody over 18, but at the time of publication boosters were only being made available to adults over 40 and people in some additional high risk categories. We also removed a quote from a GP because, while it accurately reported their comments, we understood that it could have been held to over-simplify the science behind some vaccines.