Millions more people across the UK will now be eligible for a third booster vaccine as part of efforts to halt the spread of the new Omicron variant.

All people aged 18 and over are to be offered a Covid-19 booster vaccine after early evidence suggested that higher antibody levels may protect better against the variant.

Those over the age of 40 were already eligible, however the  Joint Committee on Vaccination and Immunisation (JCVI) is now advising that all adults aged 18 to 39 should be offered a booster dose.

Under new advice people who have received their second dose will now have to wait just three months for their third as opposed to the current six-month wait, the JCVI added.

Confirmed Omicron variant Covid cases in the UK

Increased likelihood of a “mismatch” between current vaccines

Professor Wei Shen Lim, chair of the JCVI told the briefing there was an increased likelihood of a “mismatch” between current vaccines and the variant, which may reduce the effectiveness of vaccines.

But he said a boost of either Moderna or Pfizer could really push up the immune response and cutting the time between doses could mitigate any drop in vaccine protection.

“If we can raise the level of immune response of the vaccine, that higher level of immune response will reach out and provide an extra level of protection to mismatched variants,” he said.

The expert said there was also a need to deploy booster vaccines “before the wave starts” with any new variant, which is why the new expansion of the vaccine programme is being brought in.

Swindon Advertiser: Covid-19 vaccine doses in the UK. (PA)Covid-19 vaccine doses in the UK. (PA)

How to book your Covid booster vaccine amid spread of Omicron variant

With new guidance from the JCVI, the NHS is working on rolling out a booster programme.

An NHS spokesman said the new groups of people who are eligible for the booster vaccine will be invited to get a jab and the system is working “at extreme pace to respond to this new variant and to put in place the next and most complex phase” of the vaccination programme.

The NHS spokesman said: “The NHS will shortly set out how staff will expand the booster programme – this will include how booster jabs will be given in priority order so that the most vulnerable people are protected first, while also increasing capacity to vaccinate millions more people in a shorter space of time.

“The NHS will contact you when you are due to book in for your lifesaving booster vaccination, and when you get the call, it’s vital that people come forward as quickly as possible.”

Swindon Advertiser: People will be invited by the NHS to book their jab. (PA)People will be invited by the NHS to book their jab. (PA)

When invited, people will be able to book in at a vaccination centre or pharmacy site through the national booking service.

Text invitations appear as an alert from “NHSvaccine” and include a link to the NHS website to reserve an appointment.

People who cannot go online can call the service on 119 instead to book their jab.