What do we know about the role of schools in the COVID-19 pandemic? Five experts respond
The issue of school closures has been the subject of recurring debate since the start of the Covid-19 epidemic. It is now clear that severe forms of the disease only affect children in very exceptional 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 epidemic? To understand this, we interviewed five experts.
Lionel Cavicchioli, The Conversation
"In our models, we do not consider children to have a different profile from adults."
Mircea Sofonea, Associate Professor of Epidemiology and Evolution of Infectious Diseases at the University of Montpellier
Assessing the contribution of children to the dynamics of the epidemic has been a crucial issue in our understanding of the epidemic from the outset, but it faces significant methodological difficulties and raises legitimate questions about the cost-benefit balance of measures targeting schools. On this specific issue, the conclusions of the studies have not all been consistent. Some French references initially downplayed this impact, prior to the results ofthe ComCor study by the Pasteur Institute, while German and British references were more pessimistic. According to the Germans, viral loads are as high in children as in the rest of the population, which has been confirmed more recently 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 has emerged on their territory reproduces more easily in younger people than the historical strain, which we have also observed in France.
One of the difficulties is obtaining data on these age groups and being able to distinguish between hyper-contagiousness (risk of transmitting the infection) and hyper-susceptibility (risk of developing the infection when exposed). As most young children are paucisymptomatic (show few symptoms) or asymptomatic, they do not meet the criteria for screening (the French Pediatric Society has limited the indications for PCR screening for children under six years of age), which restricts the possibility of identifying and breaking chains of transmission in schools.
Another difficulty is that it is complicated to determine the actual contact rate of children and adolescents. But one thing is certain: by definition, children have more contacts than other age groups because they are exposed to their peers. Should this overexposure be taken into account? Personally, I am in favor of a rather cautious and conservative approach, in other words, not considering 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 make children more or less contagious or more or less susceptible than adults (on the other hand, we do not include them in the same way in hospitalization models, obviously, since severe forms of the disease only affect them in very exceptional cases).
With regard to the implementation of restrictions, it is clear that schools are places where infection can spread, and closing them is an effective way of slowing the epidemic. However, they are also too essential to be considered a primary target for restrictive measures.
"We tend to think that children will be less likely to transmit the virus because they are asymptomatic."
Pascal Crépey, epidemiologist and biostatistician at the École des Hautes Études en Santé Publique (School of Advanced Studies in Public Health)
What is clear is that it is difficult to track the dynamics of infection in schools, mainly because children do not develop severe forms of the disease, and few develop symptoms. Unless they are tested very regularly, whether they have symptoms or not, it is difficult to get a clear picture of the dynamics.
The question that needs to be answered is, "Do children contribute more significantly than adults to the dynamics of the epidemic?" This is what would justify targeting them as a priority for restrictive measures.
However, the dynamics of influenza teach us that people without symptoms, even if they do not isolate themselves, are less contagious than sick people. This is because they do not cough or sneeze and therefore excrete fewer viral particles. Furthermore, although studies differ, their viral load is also lower, which means that, in principle, they also have fewer viruses to excrete.
Based on this, we tend to think that children will be less likely to transmit the virus because they are asymptomatic. However, this is offset by the fact that children have a lot of contact with each other and are less likely to respect physical distancing, mask wearing, hand washing, etc. Nevertheless, since schools reopened, health protocols have been put in place. Although compliance may vary from school to school, these protocols further limit the spread of infection in schools.
Given that the British variant is more transmissible than the original strain in all age groups, we can expect to see an increase in infections among younger people, but this will be similar to the increase seen in the rest of the population. The proportion of infections attributable to children will not change.
In recent weeks, there has been a particularly significant effort to carry out testing in schools. Between week 10 and week 11, the number of tests carried out increased by 40%. This increase has led to a rise in incidence, as more positive tests are being found. However, the incidence among 10-14 year olds remains lower than the incidence among adults. There are therefore infections among children, but they are less numerous than in the adult population.
"The question of keeping schools open is above all a question of balancing the benefits and risks."
Christèle Gras-Le Guen, professor of pediatrics, president of the French Society of Pediatrics
One year on, the role played by schools in the dynamics of the epidemic remains one of the areas where communication is most confusing and difficult.
No one disputes that schools are a potential source of infection and could harbor infectious outbreaks: we have said that children are not very contagious, but we have not said that they are not contagious at all. However, we have observed that, in general, children tend to be infected by adults; the reverse is rarer. It is not impossible, but there is a difference between what is possible in theory and what we see in practice. We see that infections occur mainly within the family (meals and private gatherings).
See also:
One year later, what do we know about SARS-CoV-2 coronavirus infection in children?
We 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 circulation among children and adolescents is much lower than among adults, but also that very few classes have been closed and very few clusters have been investigated in schools. In addition, figures from the Ministry of Education indicate that very few teachers have been infected.
One area where data is lacking is the question of the contagiousness of asymptomatic children and their proportion. Until now, children who have been tested have been tested either because they had been in contact with a positive case or because they were symptomatic, but no systematic testing has been done on asymptomatic children. The introduction of saliva tests in schools has made it possible to better describe the transmission of the virus in the absence of symptoms in children. The French Ministry of Education's bulletin indicates that of the 200,404 tests carried out between March 15 and 22, only 0.49% of students were positive and therefore potentially contagious, confirming that asymptomatic children make only a marginal contribution to the spread of the epidemic.
Martin Bureau / AFP
This is not to say that there is no risk of an epidemic in schools. However, it is minor compared to the expected benefit to children's health 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 people has been particularly affected by the health crisis. The question of keeping schools open is above all a question of balancing the benefits and risks, which must be adapted to the level of virus circulation and the age of the children, and is the last measure to be taken when all else has failed (strict lockdown, optimized barrier measures, intensified vaccination of childcare professionals).
"Schools play a role in the dynamics of the epidemic."
• Dominique Costagliola, epidemiologist and biostatistician, deputy director of the Pierre Louis Institute of Epidemiology and Public Health
I completely understand that it may be decided that it is important, for many reasons, for children to continue going to school.
However, a policy that states that "schools must remain open" requires measures to be put in place to properly manage the risk associated with this decision (ventilation, masks, distancing, testing, etc.).
However, given the current high level of virus circulation, I am not sure that this is possible. It is important to emphasize that the results published in reputable scientific literature have clearly shown that schools play a role in the dynamics of the epidemic.
On this subject, one point stands out: how is it possible that we have tolerated the definition of a contact case in schools being different from that 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 tests positive in a class, the other children are not considered high-risk contacts "because they are not very active in the chain of transmission of the virus." A class was only closed if there were three confirmed cases. Things have changed recently in departments that are back in lockdown: all classes will be closed "as soon as the first case is detected.")
This definition of a contact case suggested that there was no problem in schools. Abroad, in Germany and England, schools were closed when strict measures were decided upon. In an opinion piece published on February 24 in the newspaper Le Monde, Mélanie Heard and François Bourdillon emphasized the importance of recognizing the role of schools in the dynamics of the epidemic.
"If we want to keep schools open while better controlling the epidemic, we must ensure that protocols are effective."
• Vittoria Colizza, Inserm Research Director at the Pierre Louis Institute of Epidemiology and Public Health
The susceptibility of children and their role in the dynamics of the epidemic were issues that were studied very early on in the pandemic.
To date, the conclusions of this research remain unchanged: individuals under the age of 20 are less likely to be infected, and young children are less contagious.
There was probably an initial misunderstanding: some people may have believed that children at school did not catch the disease. This is not the case, as confirmed by the work of Arnaud Fontanet's team at the Pasteur Institute, which looked at the risk of infection among students according to age. However, most cases went unnoticed because they were asymptomatic. Cases were only detected when a symptomatic case occurred, or after an investigation to trace contact cases in an infected household, for example.
See also:
Covid-19: schools and infections, what does science say?
The only new development in recent months is that the British variant is more easily transmitted and causes more severe forms of the disease, which—in conditions of high incidence such as those currently seen in France—means that more cases are now being detected in schools. Furthermore, as the virus is circulating less elsewhere because many places are closed and people are working from home, infections in schools are inevitably becoming more significant.
One thing is certain: if we want to keep schools open while better controlling the epidemic, we must ensure that the protocols in place are effective.
Our latest work, conducted with Alain Barrat's team (CNRS), aimed to understand whether regular screening in schools would reduce the number of cases. Based on contact data collected in a school with 250 students, we built a model of the spread of the epidemic within this school located in a department under renewed lockdown. This model enabled 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 screening scenarios (PCR on nasopharyngeal swabs, PCR on saliva samples, antigen testing on nasopharyngeal swabs).
Closing the class according to the standard protocol reduces the number of cases within the school by 10 to 20% over a quarter. We compared this protocol with regular testing protocols: testing once every two weeks, once a week, twice a week, and every school day. We found that the key parameter is not the sensitivity of the tests, but the frequency of screening and adherence.
If only a quarter of students participate (low uptake, in the case of unpleasant nasopharyngeal tests, etc.), testing would have to be carried out almost every day to identify cases and thus further reduce the spread of the epidemic. If three-quarters of students participate (in the case of saliva tests, which are less unpleasant), the same level of reduction in the impact of the epidemic can be achieved by conducting only one test per week.
If we want to keep schools open as much as possible, we need to move towards this type of protocol, which is much more effective than the current one. With the current protocol, classes are generally closed too late, which does not prevent the virus from spreading to other classes. In Switzerland, some cantons carry out tests every week. In the United Kingdom, self-testing has been introduced twice a week.
Lionel Cavicchioli, Health Editor, The Conversation
This article is republished from The Conversation under a Creative Commons license. Readthe original article.