A TEMPORARY "circuit break" of national lockdown measures could slow the spread of Covid-19 while buying time for NHS Test and Trace to improve, an expert has suggested.

Mark Woolhouse, professor of infectious disease epidemiology at Edinburgh University, said an "optimistic" aim of such a stop-gap measure could be to halve reduce number of new infections for a short period.

But he warned that the approach would only defer the challenges of the pandemic.

It comes amid reports that Prime Minister Boris Johnson is considering a short-term 'circuit breaker' lockdown in England - including temporary closures of pubs and restaurants or shortened trading hours - to give the country "breathing space" amid a sharp rise in cases.

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It would be up to devolved governments in Scotand and Wales to decide whether to roll out any similar measures.

Discussing the concept of a "circuit breaker" lockdown, Prof Woolhouse said: "The aim is to use additional social distancing measures to reduce the R number well below one for a short period; two weeks has been suggested.

"That would drive down the incidence of new infections, perhaps by as much as half if R fell to a similar value as during lockdown, though that may be optimistic.

"Lower incidence means lower risk of infection and, for the minority most vulnerable to Covid-19, lower risk of severe illness, although the latter benefit might not be seen until after the circuit breaker was over."

Other experts highlighted that further measures would only control, rather than stop, transmission of the virus, and questioned whether a limited lockdown period of two weeks would be effective.

Data released by the Government Office for Science and the Scientific Advisory Group for Emergencies (Sage) shows the estimate for the R value - the reproduction number of coronavirus transmission - across the UK is between 1.0 and 1.2.

Prof Woolhouse said that after two weeks the rate of new cases would be expected to increase again, but take time to return to the level seen before measures were introduced.

He added: "Exactly how long would depend on the measures kept in place after the circuit breaker.

"The expectation is that all this will buy several weeks of time which could be used, for example, to improve the performance of the test, trace and isolate system. "

An advantage of the circuit break approach is that it can be planned for, in contrast to earlier lockdowns, bringing less disruption to businesses and the economy, Prof Woolhouse said.

But he warned: "As with all lockdown-type interventions a circuit breaker only defers the problem. It does not guarantee that we wouldn't need another one in the future, and so on."

Rowland Kao, professor of veterinary epidemiology and data science at Edinburgh University, said two weeks would not be enough time to assess the effectiveness of any new restrictions, and may end up causing disruption without delivering the benefits of a full lockdown.

He said: "While a two-week lockdown will undoubtedly reduce the infection rate, the danger is that it is uncertain whether something less than the total lockdown of March will have enough of an impact to actually reduce R below one under the current circumstances - for example, if schools and universities are allowed to continue to operate with in-person contact.

"If it does not, the pressures on Test and Trace and the risks to the vulnerable, including those in hospitals, will only continue to increase.

"Crucially, two weeks will be insufficient time to fully assess the impact of those restrictions. Even if R drops below one, cases will continue at similar levels for some time.

"Thus, for the slowing down effect of the 'circuit break' to be helpful, this would require that there be enough time for the current Test and Trace difficulties to be resolved. Two weeks is unlikely to be enough for this."

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The potential for the hopitality sector to face new restrictions - with curfews already in place in north-east England - comes after research suggested that August's 'Eat Out to Help Out' scheme may have contributed to a rise in infections.

Research by Oxford University found that there were twice as many diners in restaurants on Mondays to Wednesdays when the discount was available in 2020 and there had been for the same periods in 2019.

In relation to the English regions, they concluded that "there is a loose correlation between uptake of the scheme and new cases in the last weeks of August", adding: "Again, this isn’t to say that the scheme caused those cases.

"But it certainly didn’t discourage those people from going out."

Jonathan Ball, professor of molecular virology at Nottingham University, said: "It does seem ironic that after encouraging mass attendance at pubs, cafes and restaurants through Eat Out to Help Out, that we are now contemplating restricting or closing those activities down."

But UK Health Secretary Matt Hancock said another national lockdown would be the "the last line of defence", with local interventions prioritised.

"It isn't something that we ever take off the table, but it isn't something that we want to see either," he said.