Lockdown could last until summer, No 10 warns as experts warn relaxation of rules could trigger new Covid wave

England could remain in lockdown through the spring and into the summer, Downing Street has suggested, as leading scientists warned that the early lifting of restrictions may result in a “disastrous” resurgence of Covid-19.

Boris Johnson said it was “too early to say” when measures would be relaxed, with No 10 later refusing to rule out the possibility of lockdown continuing beyond Easter.

Although the UK is making strong progress in its vaccine rollout – just under 5 million first doses have been administered so far – experts have insisted that the vaccine should not be seen as a “magic bullet”.

New scientific modelling suggests that even with an uptake rate of 90 per cent among the UK’s top priority groups, as outlined by the Joint Committee on Vaccination and Immunisation (JCVI), up to 1 million at-risk people would remain vulnerable to the disease.

A lack of protection among these individuals may be enough to fuel another wave of hospitalisations and deaths when restrictions are lifted, potentially burdening the NHS for many more months to come.

Epidemiologists warn the severity of this pressure will be heightened if measures are eased too quickly once phase one of the rollout, which targets all nine groups of the JCVI’s priority list, is completed.

They have instead called for a gradual and prolonged transition out of lockdown, arguing that restrictions should not be eased until May at the earliest.

After initial hope that the vaccines would restore some degree of normality by spring, the latest science indicates that the UK still has a long way to go in bringing the pandemic under control.

Already, the organisers behind Glastonbury have announced that the festival will once again be cancelled due to the pandemic.

Under the most optimistic assumptions about the vaccine rollout, it will be several months before the population immunity threshold is reached in the UK, according to Mark Woolhouse, a professor of epidemiology at the University of Edinburgh.

His modelling assumes 85 per cent uptake, the delivery of 2 million doses a week and strict adherence to the priority groups list.

A total of 44 epidemic scenarios were simulated, each one exploring the outcome of an early lift in restrictions coupled with varying coverage rates, natural immunity levels among the population, the ability of the vaccine to prevent transmission and possible mixing patterns.

“It’s quite possible we will get a resurgence,” he said during a briefing on Thursday. “There’s no possibility up to phase one [of the rollout] that we’ve reached the herd immunity threshold and … there are still vulnerable people in the population who may get infected.”

In the scenario where there is 90 per cent vaccine uptake among the JCVI’s vulnerable groups, 1 million at-risk people will still be susceptible to Covid-19.

“It’s this 90 per cent figure that is important,” said Prof Woolhouse. “It doesn’t have to be gaps in the effectiveness of the vaccine, it’s failure to protect – it’s not that. It’s mostly about the people who haven’t had the vaccine, and if there are large numbers of them, that’s a problem.”

Matt Keeling, a professor of populations and disease at the University of Warwick, said “completely stopping all controls” in the spring would be “disastrous”.

“A complete relaxation of all controlled measures in April, not surprisingly this is a huge kick to the system,” he said. “We get massive peaks of both daily deaths and hospital admissions.

“I would be worried about any early opening of bars and restaurants, or just reducing the controls,” he said. “At the moment we’re in an unsustainable position. We can’t do anything until we’ve got the number of cases down.”

Even when vaccination for all adults is completed – which is likely to be in the autumn, according to government projections – there is still the risk of a “large sustained outbreak” once restrictions are eased, according to Prof Keeling.

In some of the epidemiological models, it was assumed that the vaccine would prove completely ineffective in preventing transmission of the virus – a possibility that is seen as unlikely by the scientists.

“If we’ve got good transmission and infection blocking” there is a higher probability that the transition out of lockdown will not be as turbulent, Prof Keeling said. However, “there’s still danger, unless the vaccine works incredibly well at stopping infection”.

He said the most realistic approach was to begin the “gradual relaxation of controls from spring onwards” – a strategy that would help to avoid overwhelming the NHS in the summer and “lower the attack rate, or resurgence” of the virus.

“If we do it too quickly we tend to have large-scale outbreaks – bigger than what we’re seeing at the moment – and so the key is slow relaxation and [hopefully] high levels of infection blocking from the vaccine.”

Dr Anne Cori, a lecturer in infectious disease modelling at Imperial College London, stressed that the extent to which the government can ease lockdown measures “really depends on the proportion of the population that is protected”, the speed of the rollout, the effectiveness of the vaccine and uptake.

Because of these different variables, she said that the vaccine should not be seen as a “magic bullet”.

All of the scientists agreed that it was likely to be September before the herd immunity threshold is reached – the point at which the R rate of the virus cannot surpass 1 – but warned that, under “pessimistic but plausible assumptions”, Covid-19 could become endemic.

Prof Woolhouse said “it depends on a number of things including coverage and key unknowns about the vaccine performance”, such as the jabs’ ability to prevent transmission and the duration of protection they offer, along with natural immunity acquired via infection.

The scientists also insisted that their models were calculated scenarios, rather than predictions, and that a lack of current data on the effects of the vaccine and uncertainty around uptake meant it was hard to draw firm conclusions about the immediate trajectory of the epidemic.

As for what the long-term future holds, Prof Woolhouse said there are “so many scenarios and different possibilities that after six months it’s really hard to say what’s going to happen”.

Earlier on Thursday, the prime minister said it was “absolutely crucial” to obey the current restrictions “in what is unquestionably going to be a tough few weeks ahead”.

The government has pledged to review restrictions, especially for schools, on 15 February, but Mr Johnson appeared to downplay hopes of an early release.

“I think it’s too early to say when we’ll be able to lift some of the restrictions,” he said, when asked about the summer.

“We’ll look at how we’re doing but I think what we’re seeing in the ONS data, in the React survey, we’re seeing the contagiousness of the new variant that we saw arrive just before Christmas – there’s no doubt it does spread very fast indeed.”

The authors of the latest React study from Imperial College London have meanwhile said that Covid-19 infections may have risen during the first week of the national lockdown, raising concern over the effectiveness of the current restrictions.

The prevalence of coronavirus across England increased by 50 per cent between early December and the second week of January, the results show.

More than 142,900 volunteers were tested between 6 and 15 January, revealing that one in 63 people had Covid-19.

“We’re in a position where the levels are high and are not falling now within the period of this current lockdown,” said Paul Elliot, lead professor of the React study.

“We’re seeing this levelling off, it’s not going up, but we’re not seeing the decline that we really need to see given the pressure on the NHS from the current very high levels of the virus in the population.”