The road to collective immunity promises to be long. An epidemiological study published Wednesday April 22 by the Institut Pasteur and carried out in a high school in Crépy-en-Valois in Oise, in one of the epicentres of the Covid-19 epidemic in France, reveals that 26% teachers, high school students and their families have been infected and have antibodies to the virus.

A level completely insufficient to justify the slightest relaxation, according to the researchers. In detail, 41% of high school students, teachers and staff working in this high school were infected with the new coronavirus during an epidemic in February-March, according to this study carried out using antibody detection tests. But only 11% of those close to the students (parents and siblings) had antibodies against Sars-CoV-2.

"No certainty"

This is far from the 60% to 70% hoped for in the general population to have sufficient group immunity to stop the epidemic, provided that the antibodies are really protective against the coronavirus and that this immunity lasts at least several months.

"We are not sure about the protective nature of antibodies", underlines Pr Arnaud Fontanet, first author of the study and head of the Epidemiology of emerging diseases unit at the Institut Pasteur in Paris.

In the case of the SARS epidemic that started in China in the early 2000s, studies had reported that 10% of patients had no more antibodies after 12 months.

"Positive Effects" of Containment

The results of this study suggest that collective immunity will not be established quickly. Especially since "other regions of France are almost free" from contact with this virus, adds the researcher.

He notes, however, "the positive effects of confinement on the slowdown of the epidemic: the school holidays in February and confinement in the Oise (intervened on March 1, before its extension to the country on March 17) greatly reduced traffic. virus in the weeks that followed. "

The study, posted online on the MedRxiv site, was carried out from March 30 to April 3 in a high school in Crépy-en-Valois (Oise) linked to a cluster of infection cases ("cluster").

It tested 661 people. Among them, high school students, teachers, staff working in the establishment, as well as parents and brothers and sisters of high school students. A total of 171 people (25.9%) were positive for serological tests from a blood test. The infection rate is similar in both sexes.

Intra-family contaminations do not appear so frequent: the risk of being infected within the home increased from 9% to 17% for parents if the student was infected (from 3% to 21% for siblings).

The 9% of parents infected when the high school student was not given an estimate of the circulation of the virus in the adult population in Crépy-en-Valois.

The rate was only 3% in infected blood donors in two nearby blood banks.

 With AFP

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