MAINTENANCE. “Omicron goes further and will continue to mutate regularly,” assures a Covid specialist

France faces an eighth wave in phase “ascending”, said on Friday, September 30, Brigitte Autran, the President of the Committee for Surveillance and Anticipation of Health Risks (Covars), the successor of the Scientific Council. Covid infections are progressing, hospital admissions are increasing and some 17 million people who are most at risk are being encouraged to receive a new supplemental booster dose of Omicron-adapted vaccines.

Against the backdrop of an epidemic backlash, a reader western france asks us the following question: “Will the BA.1 variant be overtaken by the arrival of the BA.4 and BA.5 variants? » We take stock with Yannick Simonin, virologist and teaching researcher at the University of Montpellier (Hérault).

BA.1, BA.4, BA.5… What do we know about the majoritarian variants in France?

Omicron comprises five main sub-lineages, designated BA.1, BA.2, BA.3 (which circulate very little), BA.4 and BA.5. The sublineages BA.5 and to a lesser extent BA.4 have largely become the majority in Europe and particularly France where BA.1 has almost disappeared. This is explained in particular by a better resistance of BA.4 and BA.5 to the antibodies formed after vaccination or to a previous infection. They also possess a transmission advantage over previous members of the Omicron family.

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BA.5 has been in the majority in France since mid-June. In the latest available flash sequencing survey (conducted by Public Health France). The remaining cases are mainly BA.4 (increasing slightly) and BA.2 (stable around 1 to 2% of positive cases). Within BA.5, sub-lines tend to become the majority, like BA.5.2.

“No new variants of concern at the moment”

How can the longevity of Omicron variants be explained? Can they mutate endlessly?

Omicron and its many sub-lines have a clear advantage in terms of transmissibility and antibody resistance over all previous variants. Within this variant we find the versions of the SARS-CoV-2 virus that have the greatest ability to spread in the human population. These versions have thus outclassed the other variants, which have almost disappeared because they are disadvantaged compared to Omicron.

Also read: Covid19. “You really have to wear masks”: the eighth wave is rising in France

Omicron continues and will continue to mutate regularly. This is reflected in the appearance of numerous sublines within this variant. All of these sub-lines possess one or more mutations relative to the original variant. SARS-CoV-2 is therefore constantly evolving.

Have other new variants been discovered recently?

The new versions of the virus currently found are mainly from Omicron. No new variants of concern have been found at this time. But Omicron groups many sub-lines, some of them are more carefully monitored.

This is particularly true for subvariant BA.2.75.2, which is least recognized by the antibodies generated by previous exposure to BA.2 or BA.5 (responsible for the last epidemic waves in France).

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