What do we know about the role of schools in the COVID-19 pandemic? Five experts weigh in
The issue of school closures has been the subject of recurring debate since the start of the COVID-19 pandemic. It is now clear that severe forms of the disease affect children only in very rare cases. But what about the ability of young children to transmit the virus? Is keeping schools open problematic? Can closing them be effective? Why is it so difficult to reach a consensus on the role of schools in the dynamics of the Covid-19 pandemic? To understand this, we interviewed five experts.
Lionel Cavicchioli, The Conversation
"In our models, we do not assume that children have a different profile from adults"
Mircea Sofonea, associate professor of epidemiology and the evolution of infectious diseases at the University of Montpellier
Assessing the role children play in the dynamics of the pandemic has been a crucial aspect of our understanding of the outbreak from the very beginning, but it faces significant methodological challenges and legitimately raises questions about the cost-benefit balance of measures targeting schools. On this specific issue, the conclusions of studies have not all pointed in the same direction. Some French studies initially downplayed this impact, prior to the results ofthe Pasteur Institute’s ComCor study, while German and British studies were more pessimistic. According to the Germans, viral loads are as high in children as in the rest of the population, a finding recently confirmed by American research. A British report estimated that the transmissibility of young people (up to age 16) is more than twice that of adults. Our neighbors across the Channel are all the more pessimistic because the variant that emerged in their country spreads more easily among younger people than the original strain, a phenomenon we have also observed in France.
One of the challenges is obtaining data on these age groups and distinguishing between increased transmissibility (the risk of transmitting the infection) and increased susceptibility (the risk of developing the infection given equal exposure). Since younger children are mostly paucisymptomatic (have few symptoms) or asymptomatic, they do not meet the criteria for testing (the French Society of Pediatrics has, in fact, limited the indications for PCR testing for children under six), which limits the ability to identify and break transmission chains spreading through schools.
Another challenge is that it is difficult to determine the actual rate of contact among children and adolescents. But one thing is certain: by definition, children have more contact than other age groups because they are exposed to their peers. Should this increased exposure be taken into account? Personally, I favor a rather cautious and conservative approach—in other words, I do not believe that children have a different profile from adults.
Unlike other teams, such as Vittoria Colizza’s, we did not focus specifically on schools. However, in our models, we do not treat children as being more or less contagious or more or less susceptible than adults (though we do not include them in the same way in hospitalization models, of course, since severe cases are extremely rare among them).
When it comes to implementing restrictions, it is clear that schools are places where the virus spreads, and closing them is an effective way to slow the spread of the epidemic. However, schools are also too essential to be considered a primary target for restrictive measures.
“People tend to think that children are less likely to spread the virus because they often have asymptomatic cases”
Pascal Crépey, epidemiologist and biostatistician at the École des Hautes Études en Santé Publique
What is clear is that it is difficult to track the spread of the infection in schools, mainly because children do not develop severe cases, and few show symptoms. Unless they are tested very regularly, whether or not they have symptoms, it is difficult to get a clear picture of how the infection is spreading.
The question that needs to be answered is, “Do children play a greater role than adults in the spread of the epidemic?” That is, in fact, what would justify targeting them as a priority for restrictive measures.
However, our understanding of how the flu spreads tells us that asymptomatic individuals, even if they do not self-isolate, are less contagious than those who are sick. This is because they do not cough or sneeze and therefore shed fewer viral particles. Furthermore, although studies vary, their viral load is also lower, meaning that, in principle, they also have fewer viruses to shed.
Based on this, there is a tendency to think that children will be less likely to spread the virus because they often have asymptomatic cases. However, this is offset by the fact that children have a lot of contact with one another and are likely to be less diligent about physical distancing, wearing masks, and handwashing… Nevertheless, since schools reopened, health protocols have been put in place. Even though compliance may vary from one school to another, these protocols further limit the spread of the virus in schools.
Given that the UK variant is more transmissible than the original strain across all age groups, we can expect to see an increase in infections among younger people as well, though the increase will be of a similar magnitude to that seen in the rest of the population. The proportion of infections attributable to children will remain unchanged.
In recent weeks, there has been a particularly significant effort to conduct testing in schools. Between weeks 10 and 11, the number of tests performed increased by 40%. This increase leads to a rise in the incidence rate, as more positive test results are being identified. However, the incidence rate among 10- to 14-year-olds remains lower than that among adults. There are therefore infections among children, but they are fewer in number than in the adult population.
“The question of whether to keep schools open is, above all, a matter of weighing the benefits against the risks.”
Christèle Gras-Le Guen, professor of pediatrics and president of the French Society of Pediatrics
A year later, the role played by schools in the spread of the epidemic remains one of the most confusing and difficult issues to communicate.
No one disputes that schools are places where infection can spread and could serve as hotspots for transmission: we have said that children are not very contagious, but we have not said that they are not contagious at all. However, we see that, in general, children tend to catch the virus from adults; the reverse is rarer. It is not impossible, but there is a difference between what is possible in theory and what we observe in practice. We see that infections occur mainly within the family setting (meals and private gatherings).
See also:
One year later, what do we know about SARS-CoV-2 infection in children?
We have published an article that takes stock of the situation in France two months after the start of the school year in September. We note not only that viral transmission among children and adolescents is much lower than what is observed among adults, but also that very few classes have been closed and very few clusters have been investigated in schools. Furthermore, figures from the Ministry of National Education indicate that very few teachers have been infected.
One area where data is lacking is the question of how contagious asymptomatic children are, and what proportion of children fall into this category. Indeed, until now, children who have been tested were either in contact with a confirmed case or were showing symptoms, but no systematic testing has been conducted on asymptomatic children. The introduction of saliva tests in schools has made it possible to better characterize asymptomatic viral carriage in children. Accordingly, the Ministry of Education’s bulletin indicates that among 200,404 tests conducted between March 15 and 22, only 0.49% of students tested positive and were therefore potentially contagious, confirming that asymptomatic children’s contribution to the epidemic’s spread is marginal.
Martin Bureau / AFP
This is not to say that there is no risk of an outbreak in schools. However, that risk is minor compared to the expected health benefits for children of keeping schools open, so that they can lead as normal a life as possible. This is all the more important given that the mental health of young children has been particularly affected by the health crisis. The question of keeping schools open is above all a matter of weighing the benefits against the risks, which must be adapted to the level of viral circulation and the age of the children, and constitutes the last measure to be taken when all else has failed (strict lockdown, optimized preventive measures, and intensified vaccination of childcare professionals).
“Schools play a role in the spread of the epidemic”
• Dominique Costagliola, epidemiologist and biostatistician, deputy director of the Pierre Louis Institute of Epidemiology and Public Health
I completely understand that people might decide it’s important, for many reasons, for children to continue going to school.
However, a policy that states that “schools must remain open” requires the implementation of measures to properly manage the risks associated with this decision (ventilation, masks, social distancing, testing, etc.).
However, given the very high rate of transmission right now, I’m not sure that’s possible. It’s important to note that findings published in reputable scientific journals have indeed shown that schools play a role in the dynamics of the epidemic.
In this regard, one issue stands out in particular: how is it possible that we allowed the definition of a close contact in schools to differ from the one used by Santé Publique France and the National Health Insurance Fund everywhere else?
(Editor’s note: In schools, if a teacher tests positive, their students are not considered high-risk contacts “because the teacher wears a mask”—if only one child in a class tests positive, the other children are not considered high-risk contacts “because they play a minor role in the chain of transmission.” A class was only closed once three confirmed cases were reported. Things have changed recently in departments under renewed lockdown: any class there will be closed “as soon as the first case is detected.”)
This definition of a close contact gave the impression that there was no problem in schools. In other countries, such as Germany and England, schools were closed when strict measures were implemented. In an op-ed published on February 24 in the newspaper Le Monde, Mélanie Heard and François Bourdillon clearly emphasized the importance of recognizing the role of schools in the dynamics of the epidemic.
“If we want to keep schools open while bringing the outbreak under better control, we need to ensure that the protocols are effective.”
• Vittoria Colizza, Inserm Research Director at the Pierre Louis Institute of Epidemiology and Public Health
Children’s susceptibility and their role in the dynamics of the epidemic were topics that were studied very early on in the pandemic.
To date, the findings of this research have not changed: people under the age of 20 are less likely to become infected, and young children are less contagious.
There was likely an initial misunderstanding: some people may have believed that children at school did not contract the disease. This is not the case, as confirmed by research conducted by Arnaud Fontanet’s team at the Pasteur Institute on the risk of infection among students based on age. However, most cases went largely unnoticed because they were asymptomatic. Cases were detected only when a symptomatic case occurred, or following an investigation to trace contacts in an infected household, for example.
See also:
Covid-19: Schools and infections—what does the science say?
The only new development in recent months is that the British variant spreads more easily and causes more severe cases, which—given the high incidence rates currently seen in France—means that more cases are now being detected in schools. Furthermore, since the virus is circulating less elsewhere—with many places closed and people working from home—infections in schools naturally become more significant.
One thing is certain: if we want to keep schools open while bringing the outbreak under better control, we must ensure that the protocols in place are effective.
Our latest research, conducted with Alain Barrat’s team (CNRS), aimed precisely to determine whether regular testing in schools could reduce the number of cases. Using contact tracing data collected from a school with 250 students, we developed a model of the epidemic’s spread within this school, located in a department that had been placed under lockdown again. This model allowed us to compare the effectiveness of the protocol currently in place (class closure as soon as a case of COVID-19 is confirmed in a child) with various testing scenarios (PCR on nasopharyngeal swab, PCR on saliva sample, antigen test on nasopharyngeal swab).
Closing the classroom according to the standard protocol reduces the number of cases within the school by 10 to 20% over the course of a quarter. We compared this protocol with various regular testing protocols: testing once every two weeks, once a week, twice a week, and every school day. We found that the key factor is not the sensitivity of the tests, but the frequency of testing and compliance.
If only a quarter of students participate (low uptake, due to the unpleasant nature of nasopharyngeal swabs, etc.), testing would need to be conducted almost daily to identify cases and thereby further reduce the spread of the outbreak. If three-quarters of students participate (as with saliva tests, which are less unpleasant), we can achieve the same level of reduction in the epidemic’s impact by testing just once a week.
If we want to keep schools open as much as possible, we must therefore move toward this type of protocol, which is far more effective than the current one. Indeed, under the current protocol, class closures generally occur too late and do not prevent the virus from spreading to other classes. In Switzerland, some cantons conduct weekly testing. In the United Kingdom, self-tests have been implemented twice a week.
Lionel Cavicchioli, Health Editor, The Conversation
This article is republished from The Conversation under a Creative Commons license. Readthe original article.