The minimum time between a second and third jab has also been slashed in half from six months to three, and teenagers aged 12 - 15 will now also be offered a second dose.
The Joint Committee on Vaccination and Immunisation (JCVI) has made the recommendation, widening eligibility to people aged 18 to 39, as nine cases of variant were identified in the UK, opening up eligibility for millions more people around the country.
Professor Wei Shen Lim, chair of the JCVI said: “Having a booster dose of the vaccine will help to increase our level of protection against the Omicron variant.
“This is an important way for us to reduce the impact of this variant on our lives, especially in the coming months.
“If you are eligible for a booster, please take up the offer and keep yourself protected as we head into winter.”
The JCVI said that both the Moderna and Pfizer/BioNTech vaccines can be given as a booster for adults – with equal preference given to both.
It could be several weeks before there is concrete evidence on how transmissible the new variant is and whether it evades vaccines or causes more severe illness compared to the older forms of the virus.
The emergence of the new strain has sparked concern across the globe, and new stricter measures were announced for England over the weekend.
From tomorrow morning, masks will be compulsory again in shops and on public transport, and all international arrivals into the UK will be required to take a day 2 PCR test and isolate until they get a negative result.
A number of other countries have also announced stricter border measures.
Despite the concerns, on Monday morning, Ministers sought to allay fears about the risk to Christmas plans.
Health Minister Edward Argar told Sky News he is “looking forward to a Christmas spent with family and friends”, and that the rules which are coming back are a “proportionate” and “measured” response.
Health Secretary Sajid Javid similarly told families they should plan for a “great” Christmas “as normal” and insisted it was “nowhere near” time to reintroduce social distancing rules and work-from-home guidance.