Its multiplied changes worry and put France under tension.
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The Scientific Council chaired by Prof. Jean-François Delfraissy published, on December 16 and 17, an opinion on Omicron which recalls that this variant, which appeared in November 2021 in South Africa, was responsible for a massive local distribution. and an extremely rapid global spread underway, despite the presence of the Delta variant, whose planetary dominance seemed stable until then. Delta is still very active here, underlines the Council, but, thanks to the vaccination rate of the French, of whom 20 million have received a third dose, it would be leveling off.
1. Omicron’s profile
Whether it is of animal origin or born in an immunocompromised subject (land that facilitates viral mutations) is no longer important. What matters is his profile: he is extremely contagious. Its affinity for ACE2, the receptor that allows Sars-CoV-2 to enter our cells, is dramatically increased. According to a study from Kyoto University (Pr Hiroshi Nishiura), it is 4.2 times more transmissible than Delta (which was twice as much as the original strain from Wuhan, China). And according to a study from the University of Hong Kong (Dr Michael Chan Chi-wai), it would multiply 70 times faster than Delta in human bronchi! No less than 50 mutations ( once morest only 9 for Delta) created this mutant, 32 of which concern the Spike protein, with which the coronavirus attaches itself to the ACE2 receptor, the main target of the neutralizing antibodies induced by all anti-virus vaccines. -Covid-19 designed to date. Two Omicron subtypes circulate: BA.1 (majority) and BA.2 (minority), both equally infectious. Spike having changed a lot, the fear of a loss of protection of existing vaccines once morest Omicron is legitimate.
2. Current vaccine protection
The neutralizing capacity of the serum of people who received two doses of messenger RNA vaccine would be 20 to 40 times less once morest Omicron than once morest the other variants. It would still provide, six months following the second dose, 40% residual protection once morest symptomatic Omicron infection and 80% once morest a severe form. A booster dose with messenger RNA would increase protection once morest symptomatic infection to 86% and up to 98% once morest severe forms. Omicron quickly infects both the vaccinated and those who have been infected with the coronavirus, but does not cause severe forms in them and, for the moment, does not kill. How to explain it? By the existence of cellular immunity (TCD4 and TCD8 lymphocytes) induced by vaccination and not only humoral (neutralizing antibodies). We don’t talk much regarding the first, which is very real, because, unlike the other, it is difficult to measure in routine. It is not yet clear what the duration of protection for a third dose once morest Omicron will be. It is clear that the imminent arrival of specific vaccines once morest this variant will lead health authorities in all countries to maintain the booster strategy as much as necessary, until future mutants are no longer at severe risk. That day will come. Only the most fragile will then be vaccinated.
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3. The first security remains the vaccine
The purpose of a virus is to reproduce as much as it can. The more contagious it is, the less it kills its customers and the more it prospers. It is therefore not surprising that Omicron is less dangerous than its predecessors and more contaminating. The Scientific Council emphasizes that there are still people in France at risk of severe forms with this variant. 1. 6 million unvaccinated people, including people over 60 who are vulnerable to their co-morbidity. 2. 400,000 others among those 65 and over who did not recall by December 15. 3. Between 50,000 and 300,000 immunocompromised individuals. 4. 30% of people living in nursing homes who have not received a third dose. It should be added that Omicron makes obsolete the effectiveness of several antiviral monoclonal antibodies previously used once morest the coronavirus. Pfizer’s oral antiviral drug, which will not be available until February 2022, is expected to remain effective. Detection by PCR or antigenic tests is not faulted by Omicron, which will probably be the dominant virus at the end of January 2022. For now, the vaccine remains the best preventive measure.