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Very low risk of students and teachers transmitting Covid-19 at school, Australian study suggests

When epidemic control measures are in place, the risk of transmission between children is minimal, Sydney researchers found.

Students enter the campus in Sydney, Australia.
Students enter the campus in Sydney, Australia.
Image: Xinhua News Agency/PA Images

EFFECTIVE CONTACT TRACING and epidemic control measures are essential for safe opening of schools during Covid-19 pandemic, according to two studies focused on the UK and Australia, and published simultaneously in The Lancet Child & Adolescent Health journal.

In the Australian study, an analysis of data collected between January and April in New South Wales found that there were very low levels of transmissions in schools and nurseries when control measures were put in place.

Modelling the impact of UK schools reopening in September, the second study suggests that a second Covid-19 wave could be avoided in the UK, if accompanied by a test–trace–isolate programme with sufficiently broad coverage.

Children across the globe have been affected by school closures during the first wave of the Covid-19 pandemic as governments grapple with efforts to reduce transmission.

However, school closures may have detrimental effects on children’s physical and mental health and wellbeing and have the potential to increase inequality.

Here in Ireland, the government has published a detailed plan to reopen both primary and secondary schools at the end of August – with an emphasis on handwashing and cough etiquette, but without students and teachers being required to wear masks.

Although much still remains unknown about transmission in educational settings, both studies published today point to the importance of the broader context under which schools are re-opened, as well as to the need for further research on the levels of transmission in children and teenagers.

Study observing schools in Australia

The Australian study looked at real world-data from January to April tracking Covid-19 spread within 25 schools and nurseries in New South Wales, Australia.

The study found that the risk of children and staff transmitting the virus in these educational settings was very low when contact tracing and epidemic management is in place.

Although 27 children or teachers went to school or creches while infectious, only an additional 18 people later became infected (out of 1,448 contacts – a secondary attack rate of 1.2%).

In a subset of seven schools and nurseries that underwent additional investigations, the child-to-child transmission rate was found to be 0.3%, and 1.0% for child-to-staff.

The rate of staff-to-child transmission was 1.5% and staff-to-staff was 4.4%, suggesting that children are less likely than adults to spread the virus.

The findings suggest that schools and creches (known in Australia as early childhood education and care; ECEC) do not pose a high risk for onward transmission of coronavirus where effective contact testing strategies are in place.

“Our findings are the most comprehensive data that we have yet on SARS-CoV-2 transmission in schools and early years education settings,” says Professor Kristine Macartney, Director of the National Centre for Immunisation Research and Surveillance and with the University of Sydney.

Unlike many other countries, Australia kept schools open during the first wave of the Covid-19 pandemic, with guidance in place for physical distancing and hygiene. This presented an opportunity to examine how much of a threat the virus was to students, teachers, and their families.

Overall, 12 children and 15 adults were found to have attended schools or nurseries while infectious. These attendances took place across 15 schools and 10 nurseries.

Contact tracing identified 1,448 close contacts who were followed up with regular phone calls and instructed to be tested if they showed symptoms. 633 (43.7%) of these people were tested for Covid-19 after either showing symptoms or if they opted for a test (using either nucleic acid or antibody testing).

Of the 633 close contacts who were tested following symptoms, 18 were found to have Covid-19, meaning that 1.2% of all close contacts (1,448) were confirmed positive.

Modelling reopening of UK schools

The modelling study, led by researchers at UCL and the London School of Hygiene and Tropical Medicine, provides the first estimates on the levels of test-trace-isolate coverage needed for schools and wider society to reopen while avoiding a second epidemic wave in the UK.

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For effective contact tracing and isolation, assuming 68% of contacts could be traced, 75% of individuals with symptomatic infection would need to be diagnosed and isolated if schools return full-time in September, or 65% if a part-time rota system were used.

If only 40% of contacts could be traced, these figures would need to increase to 87% and 75%, respectively.

However, if levels of diagnoses and contact tracing fall below this across the UK population, reopening of schools together with gradual relaxing of the lockdown measures are likely to result in a secondary wave that would peak in December, if schools open full-time in September, and in February 2021, if a part-time rota system were adopted in September.

In either of these scenarios of continual gradual relaxation control measures and insufficient test-trace-isolate, the authors caution that the second wave could result in the reproduction number (R) rising above 1 and a resulting secondary wave of infections 2 to 2.3 times the size of the original Covid-19 wave.

In a subset of seven schools and nurseries that underwent additional investigations including antibody testing, symptom surveys and extra nucleic acid testing for the virus, the child-to-child transmission rate was found to be 0.3%, and 1.0% for child-to-staff. The rate of staff-to-child transmission was 1.5% and staff-to-staff was 4.4%, suggesting that children are less likely than adults to spread the virus.

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