The emerging Omicron variant BA.2.75.2 largely evades neutralising antibodies in the blood and resists several monoclonal antibody antiviral treatments, according to a study published in the journal The Lancet Infectious Diseases. The findings suggest a risk of increased COVID infections in the northern hemisphere’s winter, unless the new updated bivalent vaccines help to boost immunity in the population.
“While antibody immunity is not completely gone, BA.2.75.2 exhibited far more dramatic resistance than variants we’ve previously studied, largely driven by two mutations in the receptor binding domain of the spike protein,” said the study’s corresponding author Ben Murrell, assistant professor at the Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet.
The study shows that antibodies in random serum samples from 75 blood donors in Stockholm were approximately only one-sixth as effective at neutralising BA.2.75.2 compared with the now-dominant variant BA.5. The serum samples were collected at three time points: in November 2021 before the emergence of Omicron, in April 2022 after a large wave of infections in the country, and at the end of August to early September after the BA.5 variant became dominant.
The researchers found that only one of the clinically available monoclonal antibody treatments that were tested, bebtelovimab, managed to effectively neutralise the new variant.
BA.2.75.2 is a mutated version of another Omicron variant, BA.2.75. Since it was first discovered earlier this fall, it has spread to several countries but so far represents only a minority of registered cases.
A possible increase in infections
“We now know that this is just one of a constellation of emerging variants with similar mutations that will likely come to dominate in the near future,” Ben Murrell says, adding “we should expect infections to increase this winter.”
Some questions remain. It is unclear whether these new variants will drive an increase in hospitalisation rates. Also, while current vaccines have, in general, had a protective effect against severe disease for Omicron infections, there is not yet data showing the degree to which the updated COVID vaccines provide protection from these new variants. “We expect them to be beneficial, but we don’t yet know by how much,” Ben Murrell says.
Source: Karolinska Institutet
