Omicron sublineage BA.2.75.2 escapes most antibodies, a study published in The Lancet Infectious Diseases journal says. The study, led by researchers at Karolinska Institutet in Sweden, suggests a risk of increased Covid-19 infections this winter. This is likely to happen unless the new updated bivalent vaccines help to boost immunity in the population. Bivalent Covid-19 vaccines include a component of the original virus strain to provide broad protection against Covid-19 and a component of the Omicron variant to provide better protection against Covid-19 caused by the Omicron variant, according to the Food and Drug Administration (FDA).
The new study was conducted in collaboration with researchers at ETH Zürich, Switzerland and Imperial College London, United Kingdom.
Why is BA.2.75.2 more resistant to antibodies than its predecessor?
In a statement released by Karolinska Institutet, Ben Murrell, the corresponding author on the paper, said while antibody immunity is not completely gone, BA.2.75.2 exhibited far more dramatic resistance than variants previously studied. This resistance is largely driven by two mutations in the receptor binding domain of the spike protein.
Time points at which samples were collected
Antibodies in random serum samples from 75 blood donors in Stockholm, Sweden were approximately only one-sixth as effective at neutralising BA.2.75.2 compared with the now-dominant variant BA.5, the study says. The researchers collected the serum samples at three time points. Some samples were collected in November last year, before the emergence of Omicron, some were collected in April, 2022 after a large wave of infections in Sweden, and some were collected at the end of August to early September this year after the BA.5 variant became dominant.
Which monoclonal antibody was able to neutralise the new variant?
Bebtelovimab was one of the clinically available monoclonal antibody treatments tested. Monoclonal antibodies are engineered in a laboratory and are given to a person directly in an infusion. These antibodies are used as antiviral treatments for people at high risk of developing severe Covid-19. Bebtelovimab was observed to be able to potently neutralise the new Omicron subvariant.
According to the study, BA.2.75.2 is a mutated version of another Omicron variant, BA.2.75, and was first discovered earlier this fall. Since then, the variant has spread to several countries but so far represents only a minority of registered cases.
Covid-19 infections are likely to increase this winter
Murrell said in the statement that the new subvariant is just one of a constellation of emerging variants with similar mutations that will likely come to dominate in the near future. He added that people should expect infections to increase this winter.
However, some questions remain. For instance, it is not known whether these new variants will drive an increase in hospitalisation rates. In general, current vaccines have had a protective effect against severe disease for Omicron infections. But there is no data which shows the degree to which the updated bivalent Covid-19 vaccines provide protection from new variants.
Murrell said the vaccines are expected to be beneficial, but the extent to which they provide protection against Covid-19 variants is not known.
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