Who is eligible for what, and when?

Q Who is now eligible for the booster?

A The rules have not changed yet, but when they do anyone who had their second jab at least three months ago will technically be eligible. This means the vast majority of people over the age of 18.

However, health officials have stressed that they will still call people forward in age order, saying people should wait to be contacted.

Until now, only those over the age of 40, and those in priority groups were eligible – and only if it was six months since their second jab. Details of the timetable for rollout are expected today.

Q How long do I have to wait after my second jab to get the booster?

A The new advice says boosters must be a minimum of three months after the second jab.

But as the rollout will work down through age groups, most of those being offered boosters in the next few weeks are likely to have waited at least five months.

Q Where can I get my booster?

A Once the NHS has invited you for your vaccine, you should be able to book a slot online at mass vaccination centres, hospitals, pharmacies and some GP practices.

Health officials have yet to set out details of the new expanded programme, but say extra hospital sites will be opened, while some sites will be open for extended hours.

Q Which type of vaccine will I get?

A The vast majority of people will be offered Pfizer Biontech or Moderna.

A small number of people who are unable to receive this type of jab will be offered Astrazeneca.

Q What level of immunity does the booster give?

A Booster doses have been found to provide 93 per cent protection against severe disease.

At the moment, it is not known how well the jabs work against the new Omicron variant, and there may be a level of “mismatch” between vaccine and variant.

However, scientists believe that the jabs are still likely to prevent severe disease.