TORONTO -- Effective contact tracing and virus testing are essential for the safe reopening of schools during the COVID-19 pandemic, according to two new studies.

The studies, published Monday in The Lancet Child & Adolescent Health journal, found that there are low levels of coronavirus transmission in schools when public health measures are in place.

The first study used modelling data to analyze whether a second wave of infections could be avoided in the U.K. if safety measures are enhanced in schools as they reopen. The second study analyzed real-world data from the first wave of COVID-19 infections in New South Wales, Australia to understand virus transmission in schools and nurseries.

Both studies concluded that schools can operate safely if effective virus control measures are in place.

In a linked commentary discussing the studies, London School of Hygiene and Tropical Medicine professor W. John Edmunds said both studies provide other countries with potential options on how to keep schools open amid the pandemic.

However, without knowing age-related differences in susceptibility or how COVID-19 transmits between children, he said more research is still needed.

"We urgently need large-scale research programmes to carefully monitor the impact of schools reopening… Only in this way can we take the most appropriate measures to mitigate the risks and allow us to reassure parents, pupils, and teachers alike that schools are safe to attend," Edmunds said.

Edmunds added that both studies point to the "clear importance of adequate contact tracing and testing" needed to ensure schools remain a safe place for students and staff.

"There are no quick fixes to this terrible pandemic. However, it is becoming increasingly clear that governments around the world need to find solutions that allow children and young adults to return to full-time education as safely and as quickly as possible," Edmunds said.


The first study, led by researchers at University College London and the London School of Hygiene and Tropical Medicine (LSHTM), found that a second wave of infections in the U.K. could be avoided with increased levels of testing, contact tracing and isolation measures as schools reopen.

Assuming 68 per cent of virus contacts could be traced, researchers reported that 75 per cent of children with symptomatic infection would need to be diagnosed and isolated if schools return full-time in September. The study found 65 per cent of individuals infected would need to be diagnosed and isolated if schools resumed on a part-time basis.

If only 40 per cent of contacts could be traced, these figures would need to increase to 87 per cent and 75 per cent respectively, according to the study.

If levels of diagnoses and contact tracing were to fall below these figures across the U.K., the study found that the reopening of schools combined with the gradual relaxing of lockdown measures would likely result in a second wave approximately double the size of the original COVID-19 wave.

The study’s modelling data suggests that a secondary wave could peak in December 2020 if schools are open full-time and in February 2021 if students return part-time.

Dr. Jasmina Panovska-Griffiths, who led the study, said in a press release that it is possible for schools to safely open amid the pandemic alongside other economic reopening plans. However, she cautioned that local governments must ensure that testing, tracing and isolation capacity is increased before schools do so.

"…School reopening is likely to go hand in hand with more adults returning to work and other relaxed measures across society. Therefore, our results are reflective of a broader loosening of lockdown, rather than the effects of transmission within schools exclusively, suggesting an effective test–trace–isolate offers a feasible alternative to intermittent lockdown and school closures to control the spread of COVID-19," Panovska-Griffiths said in the release.

The study assumed that children were as infectious as adults, but since the level of infectiousness in kids is non-conclusive, researchers also re-ran the model reporting children at 50 per cent as infectious as adults. Both tests yielded the same results.

Although rates of asymptomatic transmission of COVID-19 are unclear, the study assumed that asymptomatic infections account for 30 per cent of transmitted infections.

Despite warnings of a second wave, one of the senior authors of the study Chris Bonell said schools should not remain closed.

"Our study should not be used to keep schools shut because of a fear of a second wave but as a loud call to action to improve the infection control measures and test and trace system so we can get children back to school without interrupting their learning again for extended periods of time," Bonell said in the press release.

"This is even more important in the context of opening up other areas of society."

While COVID-19 can still pose a risk to children, researchers noted that keeping schools closed for long periods of time may have negative impacts on kids including their physical health and mental wellbeing, and may also increase inequality.

The authors acknowledged that there were some limitations to the study. Although they modeled scenarios to resemble the U.K., some of the assumptions are based on data from different settings.

Researchers also noted that the study does not account for the behaviour of young people who are not in school.


The second study, led by the National Centre for Immunisation Research and Surveillance and the New South Wales Ministry of Health, tracked COVID-19 spread in 25 schools and nurseries in Australia from January to April.

The study found that the risk of children and staff transmitting the novel coronavirus in these educational settings was "very low" when contact tracing and other control measures are in place.

The study reported that 27 people -- 12 children and 15 teachers -- attended school while infected. These infections occurred at 15 schools and 10 nurseries which all temporarily closed for thorough cleaning after an infection was reported.

Researchers interviewed all those infected or their guardians at diagnosis to track their attendance at school as well as any contact with other people during the time they were infectious. Close contacts were monitored with regular phone calls and asked to quarantine for 14 days. If they began to show symptoms, they were asked to take a test.

Out of the 1,448 close contacts identified, the study reported that only an additional 18 people in three schools and one nursery later became infected.

The nursery outbreak was one of the largest, involving transmission from one adult to six adults and seven children. The study suggests that the transmission stemmed from staff rather than children and a number of children were likely asymptomatic.

However, the study noted that this outbreak occurred early on during the pandemic when testing criteria had not yet been expanded.

Unlike many other countries, Australia kept schools open when the COVID-19 pandemic hit with guidance in place for physical distancing and hygiene.

Researchers found that these enhanced safety measures, in addition to effective contact testing strategies, suggest that schools and nurseries do not pose a high risk for onward transmission of the virus.

There were some limitations to the study, the most notable being that the majority of close contacts were tested after developing symptoms. Researchers said some asymptomatic or milder cases may have been missed.

Additionally, children in New South Wales were encouraged by government and health officials to stay home and take part in at-home learning for the last few weeks of March. While schools did remain open, researched reported a drop in school attendance from 90 per cent to approximately 5 per cent.

Professor Kristine Macartney, Director of the National Centre for Immunisation Research and Surveillance, said that while the study adds valuable data about COVID-19 transmission in schools, its findings need to be viewed in context of New South Wales’ overall outbreak.

"It may be that higher rates of transmission occur in areas with higher levels of infection and where contact tracing and public health measures were not as rigorous as in Australia, where borders were closed and quarantine measures were strongly enforced," Macartney explained in a press release.

Of the total of 1.8 million children in New South Wales, only 98 children were infected between January and April, accounting for 3.2 per cent of the country’s total COVID-19 infections.

"Our findings are the most comprehensive data that we have yet on SARS-CoV-2 transmission in schools and early years education settings," Macartney said.