School closures are likely to have a relatively small impact on the spread of Covid-19 and should be weighed against their profound economic and social consequences, particularly for the most vulnerable children, according to a UK review.

The research, led by University College London (UCL), is the first to look at evidence behind many governments’ decision to shut schools and keep pupils at home.

According to the UN’s education body, Unesco, more than 90% of the world’s pupils have been affected by closures.

The UCL-led survey concludes that the evidence to support the closure of schools to combat Covid-19 is “very weak”, and statistics from influenza outbreaks suggest school closures “could have relatively small effects on a virus with Covid-19’s high transmissibility and apparent low clinical effect on schoolchildren”.

The research team reviewed 16 studies of recent outbreaks of other coronaviruses, including the 2003 Sars epidemic in mainland China, Hong Kong and Singapore, and found that school closures did not help control the epidemic.

“We know from previous studies that school closures are likely to have the greatest effect if the virus has low transmissibility and attack rates are higher in children. This is the opposite of Covid-19,” said thereview’s lead author, Prof Russell Viner, of UCL Great Ormond Street Institute of Child Health.

“Data on the benefit of school closures in the Covid-19 outbreak is limited but what we know shows that their impact is likely to be only small compared with other infection-control measures such as case isolation and is only effective when other social isolating measures are adhered to.”

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Viner, who is president of the Royal College of Paediatrics and Child Health, said the benefit gained from closing schools had to be weighed against the costs. “Children’s education is damaged and their mental health may suffer, family finances are affected, key workers may need to stay home to look after children and vulnerable children may suffer most.”

He also highlighted the need to start working out how to return students to education and keep them in school safely.

“Countries that have closed schools, such as the UK, have to now ask hard questions about when and how to open schools. Interventions in schools, such as closing playgrounds, keeping students in constant class groups/classrooms, increasing spacing between students in classes, reducing the school week and staggering school start and break times across years or classes should be considered if restrictive social distancing policies are to be implemented for long periods of time.”

Prof Neil Ferguson, of Imperial College London, who is one of the key epidemiologists advising the government, said: “While school closure as a measure on its own is predicted to have a limited effectiveness in controlling Covid-19 transmission, when combined with intense social distancing it plays an important role in severing remaining contacts between households and thus ensuring transmission declines.”

Robert Dingwall, a professor of sociology at Nottingham Trent University, said the UCL survey suggested the public health benefits of school closures were not proportionate to the social and economic costs imposed on children and their families.

“It also underlines how the assumptions used in modelling the Covid-19 pandemic may rest on very flimsy foundations in terms of scientific evidence. This work suggests that UK schools could and should begin to reopen as soon as practicable after the initial wave of cases has passed through.”

The review team included researchers from UCL Great Ormond Street Institute of Child Health, UCL Institute of Education, London School of Hygiene & Tropical Medicine, University of Cambridge and University of Sydney. The review is published in the Lancet Child and Adolescent Health journal.

A government spokesperson said: “The decision to close schools was taken in line with scientific advice on how to limit the spread of the coronavirus. We asked most children to stay at home in order to protect the NHS and save lives.

“Schools will remain closed until further notice, except for children of critical workers and the children who are most vulnerable. We will reopen schools when the scientific advice indicates it is safe to do so.”

Kevin Courtney, joint general secretary of the National Education Union, welcomed the review but said it did not warrant any change of policy. “The review indicates that school closures are effective as part of a combination of tactics of social distancing and testing. This is the evidence from China, from Hong Kong, and from a modelling study carried out in the UK,” he said.

“Everyone wants schools to be reopened as soon as is safely possible. This can only happen on the basis of sound scientific reasoning that school closure is no longer necessary for the suppression of Covid-19. We are a long way from this point. The combination of measures that the government has introduced must remain in place.”

• The headline of this article was amended on 7 April 2020 to more accurately reflect the findings of the UCL review and the article was further amended on 9 April 2020 to more accurately describe the research as a review or survey.