The Pasteur Institute believes that the immunity acquired by the many infections of the fifth wave and vaccination protects the French population from an epidemic recovery by April.
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At the moment the epidemic vice of COVID-19 seems to be loosen after a month of constant reflux of the Omicron wave carried by the sub-variant BA.1, should it fear a rebound caused by its “little brother” BA.2, whose progression is confirmed weekdays in France? The Modelizations published Wednesday 23 February By the Simon Cauchemez team, at the Institut Pasteur, release the coming horizon: “The BA2 epidemic slows down the decline in cases without generating an important epidemic rebound,” write the models.
A reassuring result that counteract the disaster scenarios that could be feared the greatest transmissibility of this Omicron subfignage with a dozen additional mutations and which caused an epidemic rebound in Denmark at the same time when the country abandoned its sanitary measures. According to the Pasteur team, BA.2 is indeed 70% more transmitted than the other sub-variants of Omicron, whose original strain, BA.1, was already much more transmitted than the Variant Delta, the majority In France between July and December 2021.
“We do not expect the epidemic rebound that we had in some countries, like Denmark, because this progression of BA.2 occurs quite late compared to the Omicron wave”, explains Simon Cauchemez, responsible for the ‘Mathematical Modeling Unit of Infectious Diseases at the Pasteur Institute. Based on sequencing Flash surveys each week by the Public Health Agency France and the continuous increase in cases Ba.2, researchers expect half of Omicron cases to be BA.2 infections in the area. February 24th. In a month, at the 16th of April, about 35% of the French population may have been infected with an Omicron virus, whether BA.1, BA.2 or BA .3, the three subfolges identified so far.
an incidence rate at ever-achieved levels
The key mechanism at work here is the very strong immunity acquired by the French population at the fifth wave thanks to infections and vaccination. “For the first time since the beginning of the pandemic, the very rapid decrease in infections is not due to strict control measures but at the level of immunity,” highlight researchers. A first permitted in particular by the slightest severity of this variant compared to the precedents.
“The assumptions that are made are quite solid in the short term: when we have been infected by Omicron, we are a priori protected against a reinfection with BA.2”, ADVANCE Simon Cauchemez. However, the wave of infections has been so important, carrying the incidence rate at levels never achieved so far – more than seven times higher at the peak of the second wave – that the French are well protected against BA.2 .
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