The expansion of the Covid-19 vaccine booster programme poses a “huge logistical challenge” for the NHS experts have said.

Health leaders said the campaign was already at its “most complex phase” even before the Government confirmed changes to the programme.

The Joint Committee on Vaccination and Immunisation (JCVI) said that all adults should become eligible for boosters and that the time between second dose and booster should be reduced from six months to three months.

Now ministers have set the challenge for the NHS to offer boosters to all adults in just 62 days.

The NHS has set out plans to increase capacity as well as call in military support and an army of volunteers.

Amanda Pritchard, NHS England chief executive, told a Downing Street press conference that the NHS was working with St John Ambulance and the Royal Voluntary Service to recruit “tens of thousands” more volunteers, and on Monday the NHS will start to recruit 10,000 paid vaccinator roles.

Saffron Cordery, deputy chief executive of NHS Providers, which represents NHS trusts, said: “The target to offer boosters to all eligible adults by the end of January presents a huge logistical challenge for the NHS, but given the potential threat from the Omicron variant, it is absolutely the right thing to do.

“There are many competing pressures. The health service is already operating at, and sometimes beyond, full stretch.

“But trusts have been at the heart of the vaccination campaign that has done so much to curb the threat from Covid-19, and will play their full part in expanding and accelerating the programme.”

NHS Confederation’s chief executive, Matthew Taylor, said accelerating the booster programme would have consequences for a service that was already stretched.

“I think we can do it but to do it will have other consequences,” he told BBC Radio 4’s PM programme.

“Everybody knows our health service is under unprecedented pressure this winter. When you take a system that is already under enormous pressure and finds it difficult to cope, and you throw something else into it, then I’m afraid it will have consequences.

“We need to be realistic about what the health service is going to be able to do when it is prioritising these booster programmes.”

Commenting on the drive for volunteers, Richard Lee, chief operating officer at St John Ambulance, said: “To date, our charity’s vaccination volunteers have provided more than 800,000 hours of their time for this vital initiative, part of well over a million hours of St John Ambulance volunteers’ support for communities on the frontline of Covid-19 – including work in hospitals and on ambulances – since the pandemic began.

“As winter begins and we face the double threat of extreme weather and significant anxiety around the new Omicron variant, we are proud to continue to play our role in supporting the NHS to respond.”

Catherine Johnstone, chief executive of Royal Voluntary Service, added: “In light of the latest guidance that all those over 18 can book their booster jabs, we are urgently calling for volunteer support at vaccination sites.

“Through the NHS volunteer responder programme, you can sign up to become a steward volunteer where you will ensure the safe and efficient flow of patients on site and play a vital role in the vaccination process.

“With the festive season on the horizon, becoming a steward volunteer will mean you are playing your part in protecting the country against Covid-19. To sign up head to nhsvolunteerresponders.org.uk.”