Wearing a mask at school: what the latest American studies say about its effectiveness

Forcing the mask on children? For a year and a half of the Covid-19 pandemic, strategies have varied depending on the country. In France, this will no longer be the case in primary school from Monday, October 4 in the departments where the incidence rate has been below the threshold of 50 for at least 5 days. This reduction, which the government justifies by the well-being of children, worries some scientists who fear an increase in contamination. Two new studies, the results of which were published Friday evening in the United States by the Centers for Disease Control and Prevention (CDC, the large American agency), rather seem to support the French choice ... even if it is difficult to 'to draw definitive certainties.

New @CDCMMWR finds schools in two Arizona counties w / oa mask requirement were 3.5 times more likely to have a # COVID19 outbreak than schools requiring masks from the start of the school year.

CDC recommends universal masking for all K – 12 schools.

More: https://t.co/suuuLNItxJ.

pic.twitter.com/zYYqXoLH3j

- CDC (@CDCgov) September 24, 2021

In the United States, the start of the school year is most often spread out between mid-July and mid-August, depending on the state.

The first study was conducted on a thousand schools in Arizona, divided into three groups: those which imposed the mask on their students and members of the staff at the start of the school year, those which did so at any time thereafter, and those which do not impose the mask (certain governors, in particular Republicans, are opposed to it).

It relates to schools in the broad sense (“schools” in the text), including colleges and high schools since we go up to grade 12 of the American education system.

3.5 times higher cluster risk

The authors looked at how many epidemic episodes with at least two positive cases were recorded from July 15 to August 31. There are 191 of them, including 16 in schools with compulsory masks at the start of the school year, 62 in those which decided it later, and 113 which have never imposed this measure. After adjusting the data, the authors of the report find that there is a 3.5 times greater risk of a “cluster” in schools which do not require pupils and staff to wear masks than in those which decided to do so from the outset. departure. These data therefore relate to the risk of an outbreak of an epidemic occurring in a school environment, and not to the number of positive cases (a cluster can include 2, 5, 20, etc.).

This is precisely the purpose of the other study, this time conducted at the county level. The authors wanted to know if the incidence rate in minors had more or less increased according to the health measures at the school. Only the constituencies where the same rule (compulsory mask or not) applied to all the schools were taken into account, i.e. 520 in total. Results ? The number of positive cases in minors has increased in all counties, but more in those without a mandatory mask (around 18 cases per 100,000 more inhabitants).

However, this study has several limitations.

To begin with, correlation is not causation and other factors may explain this epidemic resumption, even if the authors took care to adjust their results for several variables.

Then, all minors were taken into account, not just those who are in school.

Finally, the samples were small in some states.

The under 12s soon to be vaccinated?

Nevertheless, in the eyes of the CDC, these results support their recommendation to make the wearing of the mask obligatory indoors in the schools, "whatever the vaccination status".

This would also limit class closures.

Read also Anti-Covid vaccination for 5-11 year olds: why it is not for now

In the United States, as in France, adolescents aged 12 and over can be vaccinated, but younger children cannot.

Pfizer is expected to transmit its data for 5-11 to the US and European drug agencies in the coming days and weeks, and an authorization (for some or all of the children) could be issued by the end of the year. .

On the other hand, one element distinguishes France from the United States: in our country, the start of the school year does not seem to have had an impact on the epidemic for the moment, the incidence rates being down in all school age groups. .