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The epidemiologist whose modelling helped shape Britain’s coronavirus lockdown strategy has predicted a significant rise in the R number if secondary schools in England fully reopen.
Prof Neil Ferguson – who resigned from the government’s Scientific Advisory Group for Emergencies (Sage) – said the R value, or “effective reproduction number”, could increase by as much as half when secondary schools reopen.
He also suggested the country may not get back to anything close to normal until next spring.
Ferguson, who quit in May after flouting the rules by receiving visits from his lover at his home, said there would have to be some tightening up of restrictions if opening schools raises the R number.
R, or the ‘effective reproduction number’, is a way of rating a disease’s ability to spread. It’s the average number of people on to whom one infected person will pass the virus. For an R of anything above 1, an epidemic will grow exponentially. Anything below 1 and an outbreak will fizzle out – eventually.
At the start of the coronavirus pandemic, the estimated R for coronavirus was between 2 and 3 – higher than the value for seasonal flu, but lower than for measles. That means each person would pass it on to between two and three people on average, before either recovering or dying, and each of those people would pass it on to a further two to three others, causing the total number of cases to snowball over time.
The reproduction number is not fixed, though. It depends on the biology of the virus; people’s behaviour, such as social distancing; and a population’s immunity. A country may see regional variations in its R number, depending on local factors like population density and transport patterns.
Hannah Devlin Science correspondent
The government has made it a national priority to get children back into classrooms in September, amid growing unease among politicians that while most children have studied remotely, other sections of society have been allowed to open for business.
However, a modelling study found that if schools in England were to reopen safely, the government’s test-and-trace strategy would have to be rapidly improved in order to avoid a second wave of Covid-19 later this year.
Ferguson told BBC Radio 4’s Today programme that the evidence, although not certain, suggested older teenagers could transmit the disease as effectively as adults.
He said: “The risk then is that big schools, comprehensives, universities, FE colleges, link lots of households together, reconnect the social network which social distancing measures have deliberately disconnected. And that poses a real risk of amplification of transmission, of case numbers going up quite sharply.
He added: “In terms of the reproduction value, the R value, opening high schools could increase it by as much as a half, but by as little as 0.2 or 0.3, but it will go up … (and) lead to quite rapid growth of the epidemic.”
Ferguson suggested a staggered approach to reopening schools to maintain the control of transmission, with concerns that “things could get quite difficult” in the winter.
He said: “Whether we can have other alternative means of provision, children being in one week and out the other week, therefore reducing contacts in school and outside school … in my view, it is likely that some form of those measures will be necessary to maintain control of transmission.”
He added: “It will be challenging and there will be no going back to anything close to normal social interaction at least not until we get through to next spring and potentially to the availability of a vaccine.”
Other leading scientists and the NASUWT teachers’ union have previously raised concerns about the safety of the government’s strategy. The chair of the Sage sub-group on pandemic modelling, Graham Medley, meanwhile, raised the possibility that other restrictions such as shutting pubs may be needed for schools to reopen.
There are also concerns about how the government’s “protective bubbles” – designed to limit transmission by grouping pupils in classes or year groups – will work in practice, particularly among teenagers who are likely to mingle while travelling to and from school, as well as socially.
School leaders have said the rules around social distancing and school transport remain vague and unworkable. Teachers on social media have mocked the government’s “bubbles” as “colanders” after it was found that official guidance allows teachers and other staff to operate across bubbles, while siblings may be in different groups within the same school.
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