- An epidemiological study in a high school in Crépy-en-Valois reveals that 26% of teachers, high school students and their families have antibodies against the coronavirus.
- This is far from the 60% to 70% hoped for in the general population to have sufficient group immunity to stop the epidemic.
- Intra-family contaminations do not appear so frequent.
The city is at the epicenter of the Covid-19 epidemic in France. An epidemiological study * in a high school in Crépy-en-Valois, in Oise, reveals that 26% of teachers, high school students and their families have been infected and have antibodies against the virus, according to the Institut Pasteur. 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 school were infected with the new coronavirus during an epidemic in February-March, according to this study published Thursday and carried out using detection tests for antibody. But only 11% of the relatives of high school students (parents and siblings) had antibodies against SARS-CoV-2.
No certainty about the protective nature of antibodies
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," said Professor 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.
Almost free from regions
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.
However, he notes that “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. "
Infrequent intra-family contamination
The study, posted on the MedRxiv website, was carried out from March 30 to April 3 in a high school in Crépy-en-Valois linked to a cluster of infection cases (“cluster”). It was carried out by serological tests made 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, and from 3% to 21% for siblings if the high school student was infected.
Fewer smokers, but complications for them
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. Among the symptoms, the study confirms that the infection is found in 84.7% and 88.1% of people who have lost their sense of smell and taste.
The infection affected fewer smokers (7.2%) than non-smokers (28%) in this study, confirming previous observations of a very low rate of smokers in patients hospitalized for Covid-19. But "smokers, in the event of contamination, risk making more complications from the Covid-19 disease," warns Professor Fontanet.
* It tested 661 people.
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