Covid-19: Omicron variant, BA.2 … How long does immunity last between two infections?

Will the sixth wave of COVID-19 be recontamination? As Europe faces a mutation in the BA.2 sub variant, Omicron’s little brother (BA.1), health authorities are concerned about the possibility of re-infection with Covid-19. This phenomenon was of concern to the Ministry of Health at the end of last January: “It is possible that we will recontaminate ourselves with BA.2, even when we are already contaminated with Omicron,” emphasized the Minister of Health, Olivier Veran, at the group of LCI.

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Two months later, the hypothesis has been validated in the field: “We have recontaminations mainly associated with the BA.2 variant,” emphasizes François Blanchicot, president of the Syndicate of Biologists, with Medi-Dispatch. The specialist explains that most people who have now tested positive for the BA.2 subvariable have already had Omicron. This raises the question about the immunity conferred by the first infection with Covid-19 virus against the BA.2 sub variant which today relates to 73% of infections in France.

Re-infection despite immunity?

Indeed, how is BA.2 able to re-contaminate a person recently infected with Covid-19? In a case report published on March 23, the French public health authority noted the existence of “mutual protection between the two sub-strains” BA.1 and BA.2. However, on February 22, in a press release, the World Health Organization expressed surprise at this phenomenon of re-contamination: “Re-infection by BA.2 has been observed after infection with BA.1, however, preliminary data from studies of re-infection on Population level suggests that BA.1 infection strongly protects against re-infection with BA.2.”

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However, the sub-variant shows significant differences from its little brother that undermine this immunity. “There are several markers on the surface of the virus: When someone is infected, our immune memory will rely on these same markers to manufacture antibodies, explains François Blanchicot. When a new variant appears, the markers differ. So you have an immune response that is not effective in fighting off the virus and defending the infected cell. “.

Short delays between infections

The result: many re-infections were observed during particularly short periods, “sometimes ranging from a month to a month and a half” between two contaminations, as François Blanchecott describes. A new phenomenon that has not been properly explained by health authorities. In their balance sheets and other case reports, these only count “re-infection” when a person is tested again for the virus at least sixty days after their last infection. However, it now seems accepted that immunity could be shorter than that.

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According to the Union of Biologists, several categories of the population are affected by this infection. “children first”, says François Blanchicot, who explains this by the end of the compulsory wearing of masks in schools. Old people too: According to the biologist, today’s nursing homes focus on 50% of the detected sources of pollution in France.