What is the ‘R’ value and why is it so important for the easing of the coronavirus lockdown? 

What is the latest on the UK’s R0? 

The government is closely monitoring the UK’s R0. 

Last week Dominic Raab, Foreign Secretary, said it stood between 0.5 and 0.9. 

He said the overall new deaths and cases are “steadily falling”. But the Foreign Secretary insisted that “the virus is not beaten yet – it remains deadly and infectious”. 

Professor Sir Ian Diamond, the UK’s national statistician has since reiterated that the ‘R’ rate has gone up in the last two weeks as a result of the outbreak of the virus in care homes. 

But the context of the prevalence of the virus is also important, he said.

Mr Raab added: “So overall the R level is down but challenges still remain. Our top focus is on hospital infections and care home cases. We have a plan to drive numbers down of the next few months.”

Which interventions can help reduce the R0?

There are lots of infection control measures experts can use to push this number down and “flatten the epidemiological curve”. A study in the Lancet earlier this month, for instance, estimated that travel restrictions in Wuhan caused R0 to drop from 2.35 to 1.05 after just one week. 

According to a pre-print study from the London School of Hygiene and Tropical Medicine published at the start of April, the average number of people an individual comes into contact with each day dropped by 73 per cent since the UK’s lockdown began. 

“This would be sufficient to reduce R0 from a value from 2.6 before the lockdown to 0.62 during the lockdown, indicating that physical distancing interventions are effective,” the study, which tracked over 1,300 adults and has not yet been peer reviewed, concluded. The government’s more recent estimates have since backed up this data. 

So if it is working, why are we not out of lockdown yet? 

The R0 is not the only figure the government is tracking. It is also making sure that the pandemic does not overwhelm the NHS, looking for a “sustained and constant” fall in death rates, ensuring there is enough personal protective equipment (PPE), and finally, being confident that any changes do not risk another peak. 

Prime Minister Boris Johnson said the UK is close to achieving these aims – but the final test, preventing a second wave of coronavirus, comes back round to the R0 again. 

Professor Whitty has said that it was the job of the government’s Scientific Advisory Group for Emergencies (Sage) to inform the government the effect on the R value of every decision taken on lifting the lockdown. 

In Germany, where some lockdown measures were lifted once the R value made it to 0.7 – with some shops reopening, for example – concerns abated after the country’s Robert Koch Institute said that the reproductive rate had crept back up to around 0.76. 

As such, its government plans to keep many social distancing measures in place for a longer period than initially expected. It is likely that the UK, too, will have to walk a similar tightrope, lifting some restrictions while keeping a close eye on R0 and cases, and adapting its plan depending on what happens.   

In the latest guidelines, released on May 11, the Government announced a Covid Alert System to monitor infection rates and the impact of changes to coronavirus restrictions. Boris Johnson said the system would help to chart “progress and to avoid going back to square one”.

This system will be overseen by the new Joint Biosecurity Centre – and any changes to the status of the UK within the alert system will be made on the basis of the reproduction rate and the number of new coronavirus cases.  

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