There’s a lot that’s still unknown about the latest subvariant, including whether it’s more contagious than other forms of omicron, Mahon said. Other scientists worry that XB.1.5 is even better at getting around the antibodies we’ve built up from Covid vaccines and previous infection from the many different types of omicron that have spread since last December, including the original BA.1 and the more recent BQ.1.1 and BQ.1 subvariants.
The XBB.1.5 is a relative of the omicron XBB variant, which is a recombinant of the omicron BA.2.10.1 and BA.2.75 subvariants. Combined, XBB and XBB.1.5 make up 44% of cases in the U.S., crowding out other versions of omicron. XBB has been found in at least 70 countries, according to the World Health Organization, and has caused surges of infection in some parts of Asia, including India and Singapore, in October.
Studies performed in the lab have found that XBB is capable of evading antibodies from previous covid infections or vaccinations, meaning that being exposed to the virus would mean someone is more likely to get sick or reinfected and show symptoms. “It’s clear that there’s immune evasive properties of XBB,” said Dr. Isaach Bogoch, an infectious disease physician and epidemiologist at the University of Toronto.