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expert reaction to the idea of a ‘circuit break’ to suppress spread of COVID in England

In interviews this morning the Secretary of State for Health, Matt Hancock, discussed the idea of a ‘circuit break’ to suppress the spread of COVID-19 by closing down some parts of society whilst allowing others to remain open. 


Dr Simon Clarke, Associate Professor in Cellular Microbiology at the University of Reading, said:

“With a fast-increasing number of infections, it’s imperative that the country gets ahead of the curve and prevents an even more rapid acceleration.  Ideally this would be achieved by social distancing and observance of good personal hygiene, but it’s becoming increasingly clear that those measures are insufficient and unless the tide can be turned by other restrictions on our lifestyles, stricter controls like the so-called ‘circuit break’ may become necessary.

It’s true that younger people are over-represented in the new diagnoses in the UK and that they are at lower risk of developing serious disease, that picture is beginning to shift and it’s now becoming painfully clear from France that infections in low-risk groups can spread to people at higher risk. 

“The developing culture clash about whether this is a second wave, or whether testing data is significant, is losing sight of the fact that Covid-19 has the ability to put large numbers of very unwell people into hospital, very quickly, preventing healthcare systems from treating their normal caseload.  When the hospitals start filling up, who cares about the definition of a second wave?”


Prof Paul Hunter, Professor in Medicine at the University of East Anglia, said:

“Any lockdown, whether local or national, will have an impact on transmission rates and ultimately will lead to a decline in reported case numbers starting from about two weeks after the start of lockdown and continuing for about two weeks afterwards.

“The problem is that cases decline in lockdown at a much slower rate than cases increase during the period before. This can be clearly seen by looking at the graph of case reports by day in the UK.  In the 28 days up to the peak in early April case numbers were doubling about every 7 days and more rapidly than that early on. In the following 56 days cases numbers were only halving every 4 weeks though partly this was because of better availability of testing.

“So an on-off approach to lockdown is only likely to work if we have at least twice as long in lockdown as out of lockdown.”


Prof Mark Woolhouse, Professor of Infectious Disease Epidemiology, University of Edinburgh, said:

The idea of a ‘circuit breaker’ is very simple. The aim is to use additional social distancing measures to reduce the R number well below one for a short period; 2 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. 

“At the end of the 2 weeks we would expect to see incidence start to increase again, but it would take some time before it returned to its pre-circuit breaker value. 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. 

“One advantage of a circuit breaker is that it can be scheduled and planned for; in contrast to previous national and local lockdowns, we would know in advance how long it would last. That should mean that it is less disruptive to businesses and the economy.

“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.”


Prof Jonathan Ball, Professor of Molecular Virology, University of Nottingham, said:

“I haven’t seen the detailed scientific advice, but it sounds like the plan would be to control, rather than stop transmission and new cases by focussing on restricting or curtailing those activities where the evidence points to increased risk – bars and restaurants for example. I guess that’s what we’re seeing in the north east of England right now.

“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.”


Prof Rowland Kao, Professor of Veterinary Epidemiology and Data Science, University of Edinburgh, 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 – e.g.  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.”


Dr Julian Tang, Honorary Associate Professor, University of Leicester, said:

“Think of it more as a firebreak – in the sense that you cannot stop those who are already infected being infected (like trees that are already on fire in a burning forest) – but you can stop the fire from spreading to new trees (those still susceptible and uninfected).

“The various measures – rule of 6, curfews, ongoing social distancing, masking, hand-washing – all add to this firebreak effort. 

“But these are all incremental and each on their own or in patchy combinations may not be enough – in which case a full local lockdown may be needed to stop the spread.

“So again, individuals need to follow these restrictions to protect the larger population otherwise there may be a continual series of short-term leap-frogging local or national lockdowns required to control the pandemic – which will be bad for business and education over the longer term.

“We will have to compromise some individual freedoms for the greater good of the larger population.”



All our previous output on this subject can be seen at this weblink:


Declared interests

Prof Ball: no COIs

Prof Woolhouse: No COIs to declare

No others received.

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