As the UK moves into Plan B to slow the spread of Omicron, the NHS has cut the qualifying time for people in England to book their Covid booster vaccine from six months to three after the second dose of the vaccine.
Cases of Omicron have reached a tally of over 400 cases in the country.
And, though the Covid variant has been thought to evade vaccine immunity, the booster shots can still help provide long-term protection against getting seriously ill from Covid-19.
This should also reduce the number of people requiring hospitalisation due to the virus.
Here's everything you need about the booster shots.
Who is eligible for a booster jab?

Booster vaccines will be made available on the NHS for all adults in England aged 18 and over by the end of January.
Also eligible, are people living and working in care homes as well as frontline health staff and social care workers.
This is in accordance with the independent experts at the Joint Committee for Vaccination and Immunisation (JCVI), which allows anyone in the above groups to book their jab from three months after their second dose.
The new regulations mean that an additional seven million people over 40 are eligible, while younger people are being urged to wait until they’re called forward for their boosters in order of age, grouped into five-year age bands.
How to book a booster jab
Most people can either book their booster jab appointment online for a vaccination centre or pharmacy, or you can go to a walk-in vaccination site to get jabbed without needing an appointment.
Alternatively, you can also wait to be contacted by your local NHS service like a GP surgery and book your appointment with them.
Those employed by an NHS trust or a care home can typically get their boosters through their employer.
You also have the option to pre-book your booster jab only if its been two months (61 days) since your second dose.
When you book you’re likely to be offered appointments three months from the date on which you took the second dose.
Do booster vaccines protect against Omicron?

On Wednesday, December 8, Pfizer said that a booster of its vaccine may offer important protection against the new Omicron variant by increasing people's level of antibodies, even if the initial two doses appear significantly less effective.
Bharat Pankhania, a Senior Clinical Lecturer at University of Exeter Medical School told Euronews that this is “promising news” as this could mean that any vaccines could do the same as Pfizer.
He said: "If Pfizer can do it, so can Moderna and so can AstraZeneca, because what this translates into is as follows: the new variant is not so effectively neutralised by the existing antibodies."
Adding: "And what the boosters are doing, whether it is AstraZeneca, Moderna or Pfizer, is giving you a bigger number of antibodies to neutralise the virus."