UK Edition
Reopening schools without an improvement in test and trace could result in a second coronavirus wave more than twice the size of the first, a Lancet study suggests.
Researchers said pubs may have to be closed or millions of people urged to work from home if significant progress in tracking the spread of the virus is not made in the next month.
The study, by University College London and the London School of Hygiene and Tropical Medicine, simulated how the virus might spread when schools open at the start of September. It found that, if test and trace was more successful – so that 68 per cent of the contacts of positive cases were traced – the spread could be held in check.
Researchers warned that just 50 per cent of contacts of positive cases are currently reached. They said only one in seven infections in the country is being detected by the programme when its results are compared with surveillance sampling.
Without improvements, the opening of schools and associated changes such as the return of parents to work could result in a second wave (see video below) this winter that is two to 2.3 times the size of the first, they said.
On Friday, the chief medical officer, Professor Chris Whitty, said Britain has "probably reached the limit of opening up society" and would need to make "difficult trade-offs" in order to allow schools to open on September 1.
Experts warned that this could mean pubs being closed and households ordered not to mix, either on a national basis or in areas seeing a surge in coronavirus cases.
On Monday, scientists said it was "absolutely essential" that such measures are introduced if major improvements in the effectiveness of test and trace are not seen.
Lead researcher Dr Jasmina Panovska-Griffiths, of the Institute of Epidemiology and Health Care at UCL, said: "Our modelling suggests that, with a highly effective test and trace strategy in place across the UK, it is possible for schools to reopen safely in September.
"However, without sufficient coverage of a test-trace-isolate strategy the UK risks a serious second epidemic peak either in December or February. Therefore, we urge the Government to ensure that test-trace-isolate capacity is scaled up to a sufficient level before schools reopen."
Researchers stressed that the modelling, published in The Lancet Child and Adolescent Health, was based on a number of assumptions including the return of around 70 per cent of workers to the workplace when schools are back.
Much of the increase in infections modelled was associated with these changes rather than transmission of the virus within schools, they said.
On Saturday, Professor Graham Medley, who chairs the Scientific Advisory Group for Emergencies (Sage) sub-group on pandemic modelling, suggested pubs may have to close to allow schools to reopen.
Researcher Professor Chris Bonell, a professor of public health sociology at the London School of Hygiene and Tropical Medicine, said: "The logical approach would be to maintain restrictions where the adverse consequences are less severe than keeping schools closed."
Boris Johnson has encouraged workers to start returning to their workplaces as long as employers have made their premises Covid-secure.
But Prof Bonell suggested that keeping staff at home should be considered, alongside closing pubs and leisure facilities, in order to keep the reproduction 'R' rate of coronavirus down.
He said: "Where people can work from home – and most major companies think that's a no-brainer – if you can continue to work from home that is one way [to keep the 'R' rate down]; hospitality and leisure are other ways."
Prof Bonell said that overall, test and trace was only contacting around half of those who should be reached after a person is found to be positive.
In total, around four in five of those who test positive are reached by contact tracers, of whom around four in five pass on contacts. Of those, around three-quarters of contacts are reached, equating to overall coverage of 50 per cent.
Researchers said far too few people were being tested (see video below) in the first place.
Prof Bonell said: "It looks, from the ONS data, like there are about 4,200 new infections per day. And it looks like, from the testing data, there are about 4,200 testing positive per week. So it looks like about one in seven. So that's not good enough, basically."
A Government spokesman said: "We have rapidly built, from scratch, the largest diagnostic testing industry in British history.
"Over 16 million tests have been delivered so far, and we have the capacity to carry out more than 330,000 tests per day, growing to 500,000 per day by the end of October.
"Plans have been put in place to ensure schools can reopen safely. Local health officials, using the latest data, will able to determine the best action to take to help curb the spread of the virus should there be a rise in cases."
Meanwhile, Australian research published in the same journal suggested that fewer than one in 200 children and teachers catch Covid-19 even if they are a close contact of someone with the virus.
The study of 25 schools and nurseries shows that even though 27 children and teachers went to school while infectious, just 18 people contracted the virus.
The research, by the University of Sydney and the National Centre for Immunisation Research and Surveillance, found that, overall, those infected had close contacts with 1,448 people, an "attack rate" of just 1.2 per cent.
When one nursery outbreak was excluded from the data, it amounted to an infection rate of just 0.4 per cent, researchers said.