Covid-19: schools, really a hotbed of contamination? | Press room

Numerous studies have been published concerning the ability of children to be infected and their contagiousness. Credit: Adobe Stock

Colleges and high schools reopen their doors today, a week after primary schools. Despite a strict health protocol, concerns persist about the risk of transmission of the virus in schools.

For months, scientists have been wondering whether schools are important places of contamination, playing a decisive role in maintaining epidemic dynamics at a high level. This question goes hand in hand with that of the risk of infection for children: the vast majority of young people have less severe forms of the disease, but are they really less likely to be infected with SARS-CoV-2? Much data has been published on the subject. In order to see more clearly and better understand the current state of scientific knowledge, Canal Détox takes stock.

Are children less at risk?

Since the start of the pandemic, many studies have been published concerning the ability of children to be infected and their contagiousness. Research has mainly focused on the dynamics of contamination in family homes, showing that children under 10 years of age are about 30 to 50% less likely to be infected than adults. This is not the case with adolescents, who are at the same risk of being infected as adults. We can also add that studies carried out in families have nevertheless shown that parents are 3 to 4 times more likely to present positive serological tests than their children.

These data should however be put into perspective with the fact that children in school have on average more contacts than adults. Although they are less likely to be infected each time they encounter the virus, they are also more likely to be exposed to it more often than adults.

One point is nonetheless consensus among scientists: even when they are infected, children develop the more often mild or asymptomatic forms of the disease. Severe cases of Covid-19 in children under 18 remain rare and are found especially in those suffering from comorbidities and immune deficiencies (especially with an inadequate interferon response).

Viral transmission at school

How contagious are children? This question is still debated, but remains difficult to decide as very little data is currently available on the viral load of children.

If we are interested in viral transmission in schools, the majority of studies that have been carried out on the subject date mostly to the end of 2020, schools having been closed during the first wave. . The results remain contradictory from one study to another, but it would rather seem to be emerging that the opening of schools contributes to the spread of the virus. It is certain that even with rules and a strict sanitary protocol, it is a place of brewing where it is difficult to limit all social contact entirely.

The French study Comcor shows, moreover, that parents of children attending nursery school or secondary school also have an increased risk of being infected. They see their risk increase by 15% when their child goes to nursery school and by 30% if he goes to primary school.

However, certain measures make it possible to reduce the risks. A very recent study in the journal Science on transmission in schools in the United States also shows that parents living with children attending face-to-face schooling are at higher risk of being infected, but that certain barrier measures such as screening for possible symptoms on a daily basis, wearing the mask for teachers and stopping extra-curricular activities help reduce this risk. The risk to professors was greater than if they were taught at a distance, but not greater than for other professions working in contact with the public.

A role for self-tests?

In order to limit the risk of transmission of the virus in schools, the Ministry of National Education, Youth and Sports has drawn up a health protocol which includes in particular the closure of the class from the first case detected.

Among the measures put in place since the start of the school year on April 26, the use of self-tests and saliva tests at school (two self-tests per teacher per week, a weekly self-test for high school students from May 10) in order to better identify and isolate positive cases more quickly. France is not the only one to rely on this approach: self-tests are also used in schools by several European countries (in the United Kingdom and in Germany in particular).

A modeling study published in the last report of the scientific council shows that such regular screenings have increasing effectiveness in reducing the size of the epidemic as uptake and frequency of testing increases. On the case study of a primary school of 250 pupils, the analysis shows that with a high adherence to screening, tests once a week would be sufficient to considerably reduce (around 50%) the number of cases, with an efficiency estimated to be 3 times greater than that of the class closure protocol in the first case detected. The number of days in attendance lost on average per pupil would also be greatly reduced.