What do we know about Covid-19 transmission in schools?

Next week children in England, Wales and Northern Ireland are set to go back to school, many of them for the first time since March. Some children in Northern Ireland returned this week and children in Scotland returned to school earlier this month. A number of cases linked to schools have already been reported in Scotland and it was announced that facemasks will be mandatory in some areas of secondary schools in Northern Ireland, Scotland and England. In Wales it will be up to councils and schools as to whether face coverings are required. 

We’ve written before about how likely children are to catch the virus themselves and how likely they are to pass it onto other people. The evidence is not definitive, but in general they seem less likely to catch it than adults, and if they do catch it they’re less likely to develop severe symptoms. But what does going back to school during the pandemic mean for children and the wider community?

There isn’t much conclusive evidence on what happens to children and coronavirus in school settings, largely because not many children have been to school since the pandemic began earlier this year. In the UK, those who have been in school were often in smaller classes so it hasn’t been possible to see what will happen when normal schooling resumes.

But the evidence we do have suggests that schools probably don’t play a major role in spreading the virus, although some risk does exist. Infections in schools are likely, and while the evidence suggests the number of infections will mostly be relatively low, some significant clusters of infection have been linked to schools around the world. Adults in the school setting (teachers, other staff, and potentially parents) risk both catching and passing on the virus, and older children seem to be linked to infections more than younger children. The overall risks are likely to be higher when the virus is already spreading more generally in the area around the school.

Studies generally conclude infections in schools are low

During the nationwide lockdown earlier this year it was largely only the children of key workers who attended schools, and from June some other students were allowed back into classrooms. Public Health England (PHE) studied them to see whether the virus spread. It found “SARS-CoV-2 infections and outbreaks were uncommon in educational settings during the first month after the easing of national lockdown in England” but did notice a strong correlation with community infection rates. It’s worth noting that this study has not yet been peer reviewed by other academics, but these findings broadly echo those of other studies available.

PHE found that there were 198 cases of Covid-19 reported in schools, and the majority of these cases were in teachers. The cases were also mainly spread across 30 outbreaks in schools.

Commenting on this study, Professor Paul Hunter, Professor in Medicine at the Norwich School of Medicine, University of East Anglia, told the Science Media Centre: “One of the particularly useful observations to come out of this new paper is that the probability of school outbreaks is related to the incidence in the general community. Consequently it is difficult to extrapolate from a study undertaken at a time when most school children were not in school, and those that were, were mainly on under 11 years old [sic], to this autumn when the general incidence may be somewhat higher.”

One study published in June looked at available literature and media reports on Covid-19 outbreaks (or ‘clusters’). It found that there were relatively few in schools, though it did note that the role of children in introducing the virus from schools into households would need to be studied further once schools began to reopen. Another Australian study found that the transmission rate amongst school students was low, although only a small number of children were involved in the study.

A report from the European Centre for Disease Prevention and Control has noted that while transmission of Covid-19 in schools across Europe seems to have been low, this may be because children are more likely to be asymptomatic, or have milder symptoms and so the cases go undetected. It conducted surveys with EU countries about infections in schools and also reviewed academic literature on the topic and concluded that: “There is conflicting published evidence on the impact of school closure/re-opening on community transmission levels, although the evidence from contact tracing in schools, and observational data from a number of EU countries suggest that re-opening schools has not been associated with significant increases in community transmission.” 

Much like Professor Hunter the study also concluded that “there are indications that community transmission is imported into or reflected in the school setting.”

But some studies have documented larger outbreaks

Other studies have found a higher level of transmission in schools and similar settings. A report of a Covid-19 outbreak at a children’s summer camp in Georgia, USA found that the virus “spread efficiently” between people of all age groups at the camp, both child attendees and adults. In this case, the study’s authors noted that there was a wider outbreak in the state of Georgia at the same time and it wasn’t possible to say how many people at the camp contracted the virus there or before/after they attended.

An outbreak at a high school in Jerusalem among pupils and teachers returning after lockdown was described as “major” and involved 153 students and 25 staff as well as a number of contacts outside the school. The authors of a study examining this case said that it may in part have been down to the heatwave in Jerusalem at the time, meaning that certain protective measures (for example wearing face masks) were waived at the time, and the fact that there were large and overcrowded classes.

One study in South Korea which looked at the rate of infection among contacts of people with Covid-19 found that children aged 10 and over had a higher rate of transmission among household contacts than those under 10. However in this case the researchers said they couldn’t know to what extent children were socialising with each other and that more research was needed “to evaluate the public health benefit of school closure as part of mitigation strategies.”

Balancing risks

Overall, while the evidence remains incomplete, there is general agreement that some transmission of the virus can (and almost certainly will) happen in schools. But the balance of evidence suggests that schools are not generally a major driver of community spread, although school-based clusters may occur, and the risk of these may rise if the general infection rate in an area is higher.

As many experts have noted, these risks need to be weighed against the potential damage to children from not reopening schools. Some uncertainty remains, and much may depend on how well protective measures (such as distancing, hand washing or face coverings) can be maintained.

All four Chief Medical Officers in each of the UK nations issued a statement saying:

“Our overall consensus is that, compared to adults, children may have a lower risk of catching COVID-19 (lowest in younger children), definitely have a much lower rate of hospitalisation and severe disease, and an exceptionally low risk of dying from COVID-19. Very few, if any, children or teenagers will come to long-term harm from COVID-19 due solely to attending school. This has to be set against a certainty of long-term harm to many children and young people from not attending school.” 

They added that where transmission of the virus to staff did occur it was more likely to be from another staff member than a pupil and that while there was some risk of transmission from pupils to their families and the community, again, outbreaks in schools were more likely when transmission in the community was higher anyway.

Professor Hunter cautioned that “whilst there is still uncertainty over the science we certainly cannot discount schools as a likely accelerator of the epidemic in the wider community.” But he added: “Nevertheless I think Professor Whitty [the Chief Medical Officer for England] is correct when he says that missing schools is worse for children than the virus.”

And Professor Liam Smeeth, Professor of Clinical Epidemiology at the London School of Hygiene and Tropical Medicine, said: “Re-opening schools is rightly portrayed as a key national priority. We simply cannot re-open more than 30,000 schools and not expect at least some adverse impact on Covid-19, and it is important to acknowledge this and ensure adequate measures are in place to keep risks as low as possible and to respond rapidly as and when local outbreaks occur. There will be some outbreaks in individual schools, and some localised geographical areas around schools may be affected. However, with everyone acting together in a strong spirit of community, these risks to individual students, to staff, and to families can be reduced.”