A number of cases, which is partly explained by the wave of contamination last winter, but which could be underestimated, according to the government public health agency.
Santé Publique France speaks of possible reinfection when a first episode of Covid is followed by a second, provided that they are spaced at least 60 days apart. Today, these are close to a million.
” The results obtained on samples taken between March 2, 2021 and April 24, 2022 show 961,550 possible cases of reinfection identified, including 96.7% since December 6, 2021 “, according to the health agency.
Two categories were more affected: adults aged 18 to 40 and health professionals, among whom women were slightly more reinfected than men.
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The responsible Omicron variant
The overwhelming majority of second episodes occurred during the fifth wave of the pandemic. The highly contagious Omicron variant is involved in almost all possible reinfections (nearly 93%), according to available and interpretable screening results.
” After a short stabilization in early January 2022, the proportion of possible cases of reinfection reported to all Covid-19 cases has steadily increased “And represented 6.9% the week of April 19, notes Public Health France.
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If before the emergence of this variant, a few cases of reinfection had been documented, the situation was in no way similar.
Public Health France puts forward several hypotheses to explain this phenomenon: a relaxation of barrier gestures, a decrease in vaccine effectiveness, several months after the last injections, or even the ability of Omicron to escape to a certain extent from immune defenses.
Since this epidemic wave last winter, the phenomenon had been losing momentum. But the latter is gaining momentum in recent weeks with the emergence of BA.2, more transmissible than BA.1 and now the majority in the country. So much so that today, about one in 12 infections is actually a reinfection.
Under-represented contaminations
An estimate that could actually be higher: according to the definition of Public Health France, a reinfection is considered as such if the two episodes of Covid are spaced 60 days apart, thus removing all cases occurring earlier, certainly rarer, but very real.
In view of the description of cases of early reinfections in the world, the French agency also questioned a reduction to 30 days of the period taken into account between two episodes of Covid.
But ” the analysis of possible reinfections occurring between 30 and 59 days shows that it is difficult to take them into account “. ” Most likely to be cases of prolonged infection rather than cases of reinfection », Specifies SPF during a press briefing.
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