The Omicron variant was first detected in South Africa in November 2021 and has since released to many countries. It is estimated that it will be predominant within a few weeks or months. The first epidemiological studies show that the Omicron variant is more transmissible than the currently majority virus (Delta variant). It can be spread in people who have had two doses of the vaccine or who have been previously infected. Researchers from the Institut Pasteur and the Vaccine Research Institute, in collaboration with the KU Leuven (Leuven, Belgium), the CHR d'Orléans, the European Hospital Georges Pompidou (AP-HP), Inserm and the CNRS, studied the sensitivity of the Omicron variant to monoclonal antibodies used clinically to prevent severe forms of the disease in people at risk, as well as to antibodies present in the blood of people vaccinated or who have already been infected with SARS-CoV- 2. They compared this sensitivity with that of the Delta variant. Researchers have shown that Omicron is much less sensitive to neutralizing antibodies than Delta. The researchers then analyzed the blood of people who had received two doses of the Pfizer vaccine or the AstraZeneca vaccine. Five months after vaccination, antibodies in the blood are no longer able to neutralize Omicron. This loss of efficacy is also observed in people infected with SARS-CoV-2 in the previous 12 months. A third booster dose with Pfizer vaccine, or the injection of one dose of vaccine in people with a previous infection, greatly increases antibody levels to a level sufficient to neutralize Omicron. Omicron is therefore particularly insensitive to anti-SARS-CoV-2 antibodies currently used in the clinic or obtained after two doses of vaccine. or injecting a dose of vaccine in people with a previous infection greatly increases antibody levels to a level sufficient to neutralize Omicron. Omicron is therefore particularly insensitive to anti-SARS-CoV-2 antibodies currently used in the clinic or obtained after two doses of vaccine. or injecting a dose of vaccine in people with a previous infection greatly increases antibody levels to a level sufficient to neutralize Omicron. Omicron is therefore particularly insensitive to anti-SARS-CoV-2 antibodies currently used in the clinic or obtained after two doses of vaccine.
The study was pre-published on the bioRxiv website on December 16, 2021. The scientific article was accepted and published online on December 23, 2021 by the journal Nature . The paper version will be published shortly.
The first epidemiological studies show an increased transmissibility of the Omicron variant compared to the Delta variant. Little is yet known about the biological characteristics of the Omicron variant. It includes more than 32 mutations in the Spike protein, compared to the first SARS-CoV-2, and was designated “Variant of Concern” or “Variant d'Inquietude” by the WHO on November 26, 2021.
In South Africa, the Omicron variant replaced other viruses within weeks and is responsible for a sharp rise in the number of diagnosed cases. Analyzes in different countries indicate that the doubling time of cases is about 2 to 4 days. More than 10,000 cases have for example been listed in England on December 15, 2021, where it should be the majority at the end of the year 2021.
In France, 347 cases of the Omicron variant have been diagnosed as of December 17, 2021 according to Public Health France, but it is estimated that this number will rapidly increase.
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