The Covid Omicron XBB.1.5 variant is now the most prevalent variant of Covid-19 in the United States, according to the Centers for Disease Control and Prevention (CDC). The variant now accounts for 41% of all new cases, more than doubling in prevalence over the past week. Scientists have identified several mutations in the XBB subvariants that could render the Covid-19 vaccines and omicron boosters less effective and cause more breakthrough infections.
Virologist Andrew Pekosz of Johns Hopkins University notes that the XBB.1.5 variant has an additional mutation that makes it more efficient at infecting people. Yunlong Richard Cao, a scientist and assistant professor at Peking University, has also published data that suggests XBB.1.5 is better at binding to cells through a key receptor, and is more resistant to Evusheld, an antibody cocktail many people with weak immune systems rely on for protection against Covid-19.
Experts are concerned that the XBB subvariants may reduce the efficacy of the omicron boosters, though Drs. David Ho and Anthony Fauci have both cautioned that the boosters still appear to be preventing severe disease. Health officials are urging the elderly in particular to make sure they are up to date on their vaccines and get treated with the antiviral Paxlovid if they have a breakthrough infection.