LONDON (Reuters) - Britain faces a second wave of COVID-19 this winter twice as widespread as the initial outbreak if it reopens schools without a more effective test-and-trace system in place, according to a study published on Tuesday.
Researchers from University College London and the London School of Hygiene and Tropical Medicine modelled the impact of reopening schools either on a full- or part-time basis, thus allowing parents to return to work, on the potential spread of the virus.
They concluded a second wave could be prevented if 75% of those with symptoms were found and tested and 68% of their contacts were traced, or if 87% of people with symptoms were found and 40% of their contacts tested.
"However, we also predict that in the absence of sufficiently broad test–trace–isolate coverage, reopening of schools combined with accompanied reopening of society across all scenarios might induce a second COVID-19 wave," said the study, published in The Lancet Child and Adolescent Health.
"Our modelling results suggest that full school reopening in September 2020 without an effective test-trace-isolate strategy would result in R rising above 1 and a resulting second wave of infections that would peak in December 2020 and be 2.0-2·3 times the size of the original COVID-19 wave."
The lead author of the study, Jasmina Panovska-Griffiths, said the test-and-trace system in England was currently reaching only about 50% of contacts of all those testing positive for COVID-19.
Panovska-Griffiths, lecturer in mathematical modelling at University College London, told BBC radio that the worst scenarios could still be avoided.
"Importantly, what we find is that it is possible to avoid a second epidemic wave if enough people with symptomatic infections can be diagnosed. Their contacts can then be traced and effectively isolated," she said.
"We are the first study that has quantified this, how much this needs to be for the UK."
Schools in Britain closed in March during the national lockdown, except for the children of key workers, and reopened for a small number of pupils in June.
However, the government says all pupils will return to school across the United Kingdom by early September with Prime Minister Boris Johnson saying it is a national priority.
"I think we all accept that test-and-trace is a programme which needs to continue to improve. There is total humility in government about that," junior local government minister Simon Clarke told BBC radio.
"We fully accept that we need to keep driving those numbers up," he said.