A study by researchers at the Statens Serum Institut (SSI) in Denmark shows evidence that the BA.2 subvariant of Ômicron can cause the reinfection of people recovered from Covid-19 within 20 days.
The result explains why people infected by the coronavirus in January, when Brazil went through the first wave of the Ômicron variant, are getting sick again.
A report by Fundação Oswaldo Cruz (Fiocruz), published on Monday (13/6), shows that the BA.2 lineage has become dominant in Brazil, replacing BA.1. There was also the detection of other strains with greater transmission potential in the country. The Fiocruz Genomic Network document is based on samples from May 20 to June 2.
“How long are we protected after a Covid infection? For Delta, protection averaged three months. With Ômicron and the new subvariants, that changed. There are reports of reinfection within 20 days,” medical epidemiologist Denise Garrett wrote on Twitter, sharing the Danish research.
In the study, published in late February on the medRxiv platform, researchers in Denmark had access to samples of approximately 1.8 million cases of coronavirus infections – regardless of variant – in the country, from 22 November 2021 to 11 of February 2022.
Using whole genome sequencing of the virus, they selected for BA.2 reinfection cases within 20 to 60 days of initial BA.1 infections, during which time the two subvariants emerged and became dominant in Denmark.
From a total of 187 cases of reinfection, 47 were identified by BA.2 shortly after an infection by BA.1, mainly among young people – with a mean age of 15 years – and not vaccinated. Most developed mild disease, without the need for hospitalization; there were also no reports of deaths.
“We have evidence that reinfections by the BA.2 subvariant can indeed occur soon after a BA.1 infection, causing mostly mild disease in young unvaccinated individuals, but they are rare,” the researchers concluded.
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