We hoped to put an end to the pandemic and the Omicron variant. While half of Europeans should have been infected by mid-March, bad news has just fallen. It is possible to be infected multiple times with the Omicron variant. Explanations.
The variant Omicron of SARS-CoV-2, identified in South Africa for the first time at the end of November, became the majority in Europe in a few weeks. In January, ten million new cases of Covid-19 were diagnosed in France. A figure certainly underestimated. If it is extremely contagious and affects a very large number of people at the same time, the Omicron variant, on the other hand, generates less severe clinical forms.
Moreover, the effectiveness of vaccines is around 70% in individuals who received the booster dose. These characteristics made it possible to limit the impact of the new variant on the hospital system. In France, the epidemic peak seems behind us and the daily number of new cases is decreasing. The world even hoped that the pandemic would end with the Omicron variant. This was without taking into account the ability of the variant to reinfect individuals. Indeed, this is revealed a recently published study.
Much higher risk of reinfection with Omicron than with Delta
The researchers of theImperial College of London analyzed the data from all the PCR testing positive for SARS-CoV-2 carried out between November 29 and December 11, 2021. Among them, there were 196,463 tests probably linked to the variant Delta and 11,329 tests likely related to the Omicron variant. Patients infected with Omicron were significantly younger than those infected with Delta. As observed in other studiespeople of African descent were more likely to be infected with Omicron.
In a previous study, a first infection was shown to confer protection against a new contamination by the Delta variant of the order of 85% for at least 6 months. By analyzing the data genetic samples, the authors of theImperial College of London were able to estimate that a first infection with Covid-19 protected much less against a second contamination by the Omicron variant : only 19%, i.e. 5.4 times less than against the Delta variant.
Effectiveness of vaccines against Omicron
The authors also assessed the efficacy of vaccines against Omicron. In accordance to data previously published, protection against symptomatic infection linked to the Omicron variant was of the order of:
- from 0 to 20% after a complete vaccination schedule;
- 55-80% post dose booster.
Currently, England suspects that one in ten new cases is due to reinfection. Knowing the risk of reinfection of individuals makes it possible to model theepidemic and to adapt the barrier measures in force as well as hospital capacities, for example.
Interested in what you just read?