Many subvariants of Omicron have been detected worldwide, but scientists are currently closely scrutinizing the XBB subvariant, which is more resistant to antibodies generated by vaccination. La Dépêche du Midi takes stock.
He has been alone for several months in the French “epidemic landscape”. The BA.5 sub-variant, belonging to the Omicron family, alone carried two waves of contamination linked to Covid-19 in France. At the start of the 2022 academic year, no other variant has established itself on a European scale, thus allowing the health authorities to fight, once again, against a variant whose properties are well known. However, the scientific community is concerned about a variant called “XBB”, identified in Asia, again from the Omicron line and likely to spread in Europe. The Midi Dispatch takes stock of this new discovery.
What do we know about this new variant?
Like any other virus, Sars-Cov-2 replicates and transforms. Today, the scientific community has identified over 300 sublineages belonging to the Omicron lineage. This is proof that in two and a half years of the pandemic, the virus has mutated many times (see box below). The XBB variant is of this caliber: it is “resulting from a combination of two sub-lineages of Omicron”, explains to The Midi Dispatch Professor Antoine Flahault, epidemiologist and director of the Institute for Global Health at the Faculty of Medicine of Geneva.
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This new strain is endowed with five characteristic mutations which “allow the sub-variants which are endowed with them to circumvent acquired immunity more to counter the attachment of the virus to our cells”, continues the researcher. In practice, XBB could thus infect our organism more easily: the variant “would be to date one of the known variants of SARS-CoV-2 that best manages to escape acquired immunity (following contamination , note) or vaccine”, explains the epidemiologist.
Where was this variant detected?
The XBB variant was first detected in Singapore, where it appears to be spreading at high speed and gradually becoming a “dominant strain”. “In Australia, it now represents 5% of sequenced samples, with very rapid and very recent growth,” comments Professor Antoine Flahault.
In addition, the first cases of contamination have been detected in Europe and the United States: this variant is therefore likely to impose itself there in turn, or even to “coexist with other sub-variants which seem to share certain common characteristics. with XBB”, continues the researcher.
Would the vaccines used today still be effective against this variant?
The researchers remain confident that vaccine immunity and that acquired by infections due to previous variants will reduce the risk of serious forms linked to this new variant.
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“Cell-mediated immunity – the one that allows our body to fight against severe forms of Covid – is not, to our knowledge, circumvented by these new variants, wants to believe Professor Flahault. Vaccines, mono and bivalent (new generation, editor’s note), should therefore continue to protect us effectively against the risks of hospitalization and death linked to Covid”.
How does a virus come to mutate?
When it enters a cell, a virus replicates: it copies itself to spread. During replication, errors can occur in the copying of the virus genome, such as a computer “bug”. But this error may or may not have a more or less significant impact on the way the virus behaves: these are mutations. A variant is thus a virus carrying one or more new mutations of the initial virus.