Covid-19: this reassuring data on the risk of infection acutely with BA.2, the sub-alternate of Omicron

One variant haunts the other…but this time without necessarily having an effect. BA.2 is a subspecies of the Omicron variant, and is in a way the “little brother” of BA.1, responsible for the very strong fifth wave in December and January. BA.2 accounted for nearly 30% of daily positive cases in mid-February, according to the latest serial survey. The majority will now, but it should not lead to a resumption of the epidemic, says the Pasteur Institute.

The most reassuring point concerns the dangers of being serious. BA.1 was significantly less virulent than the delta variant, and was prevalent until mid-December. In the event of an infection, various studies have shown that the risk of going to the hospital is 50-70% lower. This made it possible that this winter did not exceed the peak of hospitalization for each of the previous waves, despite the peak of positive cases at least eight times.

A reassuring South African study

and BA.2? It doesn’t sound more virulent than BA.1. Whether in South Africa, the United Kingdom or even Denmark, where there is already a majority, real-life data showed “no difference in severity” between the two subspecies, The World Health Organization (WHO) said February 22.

A detailed study was conducted in South Africa from December 5, 2021 to the end of January 2022. Based on these results, Posted on February 19 on medRxiv (but not yet reviewed), the risk of hospitalization “did not differ” between people with BA.1 and those who had BA.2. The relative risk was 0.96, with a confidence interval between 0.85 and 1.09. If it is less than 1, the risks are lower.

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The score is the same for the risk of being severely affected after hospitalization (relative risk 0.91, confidence interval 0.68–1.22). These results have been adjusted for comorbidities to avoid bias. They “suggest that although BA.2 may have a competitive advantage over BA.1, the clinical picture of the disease remains similar,” say the authors, who are members of the National Institute of Infectious Diseases in South Africa.

Alternative ‘Most Concern for Global Health’?

According to another study, in the UK this time, BA.2 can lower the risk of infection more sharply than BA.1. After adjusting for age, previous injuries, gender, or ethnicity. The relative risk of hospitalization with BA.2 was 0.87 (confidence interval 0.75 to 1), based on the report Published by the British Health Agency on Friday. However, these results are still preliminary and are based on a relatively small number of cases, so it is “possible that these estimates may change” afterwards.

Finally, note that a Japanese study, Not yet peer reviewed, on the contrary indicates an increased severity of BA.2. This may “disseminate faster and more efficiently than BA.1 into lung tissue,” the authors say, noting that BA.2 may be “the most worrisome alternative to global health.” But this work was performed in the laboratory on hamsters, so its results are not necessarily transferable to humans.

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