Fears are growing that Covid Plan B restrictions could return during the winter as Downing street warned of a “challenging” months ahead as coronavirus cases reached the highest daily level since mid-July.

Boris Johnson outlined a Covid Plan B at a press conference last month but confirmed there were no current plans to reintroduce restrictions as hospitalisations reached 900 on Monday.

The government is reportedly keeping a “close eye” on a descendant of the Covid Delta variant that is being seen in a growing number of cases.

The Prime Minister’s official spokesman said: “We obviously keep very close watch on the latest statistics.

“We always knew the coming months would be challenging.

“What we are seeing is case rates, hospitalisations and deaths still broadly in line with the modelling as set out a few months back now.

“The vaccination programme will continue to be our first line of defence, along with new treatments, testing and public health advice.

“But we will obviously keep a close watch on cases.

“But it is thanks to our vaccination programme that we are able to substantially break the link between cases, hospitalisations and deaths.”

Potential for a lot of ‘unnecessary’ Covid deaths

Prof Hayward, a member of the Sage scientific advisory panel, told BBC Radio 4’s World At One: “I think it’s concerning that we’ve got very high rates of infection and higher rates of hospitalisation and mortality than many of our European counterparts.”

He said waning immunity is “probably part of” the reason infections are currently high, adding there is “some evidence” protection against infection is beginning to wear off and “probably some evidence” protection against severe disease is waning to a lesser extent.

Prof Hayward added: “We shouldn’t be complacent because there is still huge potential for the NHS to come under a lot of pressure and for there to be a lot of unnecessary deaths.

“So we need to get the vaccination rates up and we need to be prepared potentially to think about other measures if things do get out of control.”

What’s Plan B?

Wandsworth Times: Vaccine passports would be needed for nightclubs and sport under Covid Plan B. (PA)Vaccine passports would be needed for nightclubs and sport under Covid Plan B. (PA)

The Government’s autumn and winter plan suggested that some measures including the mandatory use of vaccine passports and face coverings could be required in England if cases were putting unsustainable pressure on the NHS.

Should Plan B materialise in the coming months, what would it look like?

Key restrictions to be reintroduced would be face masks, working from home and Covid vaccine passports.

The Plan B proposals draw on the findings of a review into vaccine passports earlier this year, which concluded that certification could help keep events going and businesses open.

Government plans set out how all visitors aged 18 and over to certain events could be required to be fully vaccinated.

The events listed are all nightclubs, and other venues open after 1am with alcohol, music, and dancing, and indoor events with 500 or more attendees where they are likely to stand and mix to a significant degree, or move around during the event, such as music venues or large receptions.

The plan also includes outdoor, crowded settings with 4,000 or more attendees where they are likely to stand, or move around during the event, such as festivals, and any settings with 10,000 or more people, such as large sports and music stadia.

Detailing when restrictions could be introduced last month, a government document stated: "The Government recognises this causes more disruption and has greater immediate costs to the economy and some businesses than the other Plan B interventions, so a final decision would be made based on the data at the time."

It adds: "If Plan B is implemented, the Government will bring back the legal requirement to wear face coverings in some settings.

"The precise settings will be decided at the time."

Wandsworth Times: The PM's official spokesman said: "There is absolutely no plan to introduce Plan B currently. (PA)The PM's official spokesman said: "There is absolutely no plan to introduce Plan B currently. (PA)

The PM's official spokesman said: "There is absolutely no plan to introduce Plan B currently. We retain that capability if required if we believe the NHS is coming under unsustainable pressure.

"We obviously keep very close watch on the latest statistics. We always knew the coming months would be challenging."