Covid: The more contaminating BA.2 variant will not cause a new wave, according to the Pasteur Institute


CORONAVIRUS – It was the unknown at the start of 2022. Very largely in the majority in Denmark and in full progress in France, the BA.2 variant, a “little brother” of the now famous Omicron, is closely watched by the community. science and health authorities around the world.

But according to the Institut Pasteur, this sub-variant of Omicron should not cause a new wave of Covid-19. Here is the main modeling lesson published by the Institute on Tuesday 22 February.

However, BA.2 cases represent an increasingly large share of total contamination in the country (more than 14% at the beginning of February). Indeed, BA.2 is about 70% more transmissible than the other Omicron sub-variants, a characteristic that allows it to continue to spread in a context where the other variants are falling very sharply.

This is what makes researchers at the Institut Pasteur say that the progression of BA.2 “slows down the decrease in cases” at the national level. Clearly, because of him, the Omicron wave does not flow back as quickly as hoped.

To understand, you have to imagine an epidemic within an epidemic. The peak of contaminations at Omicron was officially reached on January 19, with 464,000 cases. But considering that not all patients are tested, Pasteur’s teams estimate the real peak at 630,000 cases around January 16.

On the other hand, the peak of BA.2 was later. In addition, the number of contaminations is not falling as quickly as for the other sub-variants of Omicron, which have collapsed in recent weeks, as shown in the graph below published by Simon Cauchemez, head of the team of modellers

Effective immunity…

Nevertheless, and the report makes it clear, contamination with the main strain of Omicron seems to confer immunity against its various sub-variants, BA.2 included. However, as the researchers note, “for the first time since the start of the pandemic, the very rapid decrease in infections is not due to the strict control measures, but to the level of immunity acquired thanks to vaccination and infections ”.

Which makes them say that even in the case of a significant relaxation of barrier gestures and sanitary measures, “it is not expected that the BA.2 sub-variant can generate a strong rebound in the epidemic” .

Considering its greater transmissibility, we understand why the researchers write that if the BA.2 epidemic “slows the decline” of cases, it should not “generate a significant epidemic rebound”. In the worst-case scenario of the modeling, BA.2 thus causes some 86,000 daily cases at the peak of the epidemic, much less than the figures for January.

… but until when?

Additional good news as the World Health Organization announced on Tuesday February 22 that BA.2 does not cause a more serious form of Covid anyway. According to the WHO, there is “a similar level of severity in terms of risk of hospitalization” between the sub-variants of Omicron, which supports the idea that even in the event of BA.2 contaminations, the hospitalizations and intensive care admissions should not jump.

And at the global level, no massive resumption of infections is yet to be noted, despite the presence of BA.2. This therefore supports the predictions of the Institut Pasteur.

However, there remains one last unknown, warn the authors of the report, that of the duration of the immunity conferred by an infection and/or vaccination. If this were to decline rapidly, the modeling could be called into question, at least partially. “In order to make longer-term projections, it will be important to take into account the decline in immunity over time,” they write. The fact remains that at present, BA.2 seems to have been only a passing concern.

See also on the HuffPost: Variant Deltacron, multiple mutations… when to worry?

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