The BA.2 strain of the omicron variant of the SARS-Cov-2 coronavirus, considered more transmissible than BA.1, already represents 42.5% of the samples analyzed by INSA, an increase in prevalence that virologist Pedro Simas considers to be a “normal evolution”.
“The predictive value of this indicator to identify suspected cases of the BA.2 lineage is now more robust, so it is estimated that this lineage represents 42.5% of positive samples on February 20, 2022”, says the diversity report. genetics of SARS-CoV-2 from the National Institute of Health Doutor Ricardo Jorge (INSA) released today.
According to the document, BA.2, which shares several genetic characteristics with BA.1 – two strains classified by the World Health Organization (WHO) as an omicron variant – was detected for the first time in Portugal in random sampling by sequencing in the week of December 27th to January 2nd.
“Its relative frequency has gradually increased since then”, adds INSA, noting that the sequencing data indicate that this prevalence has grown in all regions, representing over 15% of the sequences analyzed by region from 7 to 13 February. , with the exception of the Azores, where it will have started a community circulation later.
In a statement released today on this strain, WHO said that, based on available data on transmission, severity, reinfection, diagnosis, therapy and vaccine impact, BA.2 should continue to be considered a variant of concern and should remain classified. like omicron.
According to the WHO, “preliminary studies suggest that BA.2 appears to be more transmissible than BA.1”, but the organization notes that real-world data on clinical severity in South Africa, the United Kingdom and Denmark, where immunity from vaccination and from natural infection is high, indicate that “there was no reported difference in severity between BA.2 and BA.1”.
“Reinfection with BA.2 following infection with BA.1 has been documented, however, initial data from population-level studies suggest that infection with BA.1 provides strong protection against reinfection with BA.2”, also indicates the WHO.
Speaking to Lusa, virologist Pedro Simas confirmed that “BA.2 is more efficient at transmitting itself in the community than the previous one”, but considered that this lineage results from the “normal evolution of coronaviruses, with small changes that make them more competitive”.
“What will happen is that BA.2 will fill the niche of BA.1, which was dominant in Portugal”, but without causing, in principle, a large wave of infections, estimated the specialist.
“Right now, BA.2 is more efficient at spreading than its parent BA.1, but what is important is that the immunity conferred by BA.1, especially in vaccinated people, is very efficient at preventing infection. “, he added.
According to Pedro Simas, who advises the monitoring of BA.2, “there is no report that BA.2 is more virulent” than the previous lineages of the ómicron variant.
The virologist also explained that BA.2 cannot be considered a new variant of SARS-CoV-2, since it does not have biological characteristics that differentiate it from the parental lineage.
“This has a small advantage in spreading, but in terms of virulence and evasion to the immune system, it is not different enough to be considered a new variant”, said the researcher from the Institute of Molecular Medicine of the University of Lisbon.