As health authorities announce an eighth wave of the Covid-19 epidemic in the coming weeks, teams of researchers have identified a new sub-variant of Omicron which appears to be more resistant to the immunity induced by vaccines.
Since its appearance, the Omicron strain (B.1.1.529) has given rise to several sub-variants of the same name, including BA.1, BA.2 or even BA.1.1 and BA.4.6. It is today the footprint of BA.5 which dominates 83% of contamination around the globe and 95% in France. The new one has been identified as BA.2.75.2. According to several virologists, it could be “the next variant to take over”.
What do we know about this BA.2.75.2 sub-variant?
It was first identified in India in July, where it now dominates and is gaining momentum in Japan and Singapore. It is now present in fifteen countries, including Chile, England, the United States, Spain and Germany. For the time being, this new sub-variant of Omicron would represent only 0.5% of the coronaviruses sequenced throughout the world during the last three months. “It is not trivial to see that although dominant in certain regions in India, it has already emerged elsewhere in the world”, observes with L’Express Christine Rouzioux, professor emeritus of virology at the Faculty of Medicine of Necker and member of the Academy of Medicine.
“In France, the detection of BA.2.75 remains low, with a maximum of 0.3%”, indicates Public Health France in its last risk analysis on emerging variants, dated September 7. “Only 22 sequences of the BA.2.75 sub-lineage have been detected in metropolitan France”, specifies the document. But that doesn’t mean it doesn’t require increased monitoring. Other sub-variants of Omicron, initially a minority, later took over the contaminations. “The evolution of this detection of BA.2.75, throughout the territory and at the regional level, is closely monitored”, further underlines Public Health France.
Some questions still remain unanswered concerning its characteristics, in particular transmission and contamination. “We still lack a bit of hindsight, explains Christine Rouzioux, who also welcomes the international surveillance organized around the mutations of Covid-19. However, Indian scientists report that there is for the moment no increase significant in the number of direct hospitalizations in the regions where it circulates”.
Why does Omicron still dominate?
Omicron is the thirteenth variant of Sars-CoV-2 since the detection of the first strain in early 2020. This designation by the Greek alphabet had been wanted by the World Health Organization (WHO) to qualify and classify the most variants. worrying about the virus. But since its appearance last November, it seems that Omicron largely dominates. “The large Omicron family does not seem to have finished talking about it”, notes Antoine Flahault, epidemiologist, director of the Institute of Global Health and professor at the Faculty of Medicine of Geneva. “BA.1 entered in December 2021 to generate a very significant wave of contaminations, the peak of which took place at the end of January 2022 in France, followed by BA.2 in April and BA.5 in July. This last sub-variant BA.5 from Omicron is currently returning to trigger a new autumn wave in Western Europe”, specifies the epidemiologist. Several other Omicron sub-variants are of concern to the scientific community, including BA.4.6.
“The intense epidemic activity since Omicron became the dominant variant on the whole planet is due to its very high concomitant transmissibility of its immune escape capacity, points out Antoine Flahault. It seems that these two determinants explain the domination without sharing Omicron and its sub-variants around the world for ten months”. This does not mean that Sars-Cov-2 stops mutating, but that it mutates differently. “Based on what’s being detected right now, it looks like the future SARS-CoV-2 will evolve from Omicron,” the official said. New York Times David Robertson, a virologist at the University of Glasgow.
Can it thwart our vaccine immunity?
According to the first two studies, which are not yet validated by peers, one of which is Swedish-British and the other from research at Peking University, the antibody neutralizing capacity of the BA.2.75.2 subvariant is very strong, especially compared to vaccines already on the market. In other words, it could easily override our immune responses. “We have never seen a virus so resistant to neutralizing antibodies and monoclonal antibodies, which until then were effective, including against BA 5”, opines virologist Christine Rouzioux. And for good reason: it has some nine additional mutations in the Spike protein, the entry point, also called key, which allows the virus to enter our cells. This characteristic could make it more contagious.
In fact, it could blunt the effectiveness of new vaccine formulations. But according to Public Health France “the Omicron BA.2.75 sub-lineage is the subject of particular monitoring by the international community on the basis of its mutation profile, and at this stage no worrying epidemiological or clinical signal was associated”. Although it is not impossible that it happens. “The real concern is that immunity is little or even not protective against this variant. It has a real immune escape power”, concludes Christine Rouzioux.