The subvariant has been causing concern among scientists after its rapid spread in the United States in December.While the agency is awaiting additional data to verify how Evusheld works against XBB.1.5, it said it does not expect the drug to neutralize the subvariant due to similarities with other Omicron subvariants against which Evusheld does not work. XBB.1.5 is yet another descendant of Omicron and is an offshoot of XBB, first detected in October, which is itself a recombinant of two other Omicron sub-variants.The agency said it was closely monitoring the emergence of the XBB.1.5 subvariant, which accounted for 27.6% of COVID-19 cases in the United States for the week ending Jan. 7. Evusheld was first authorized in late 2021 in the United States to prevent COVID-19 infections in individuals with weak immune systems or a history of severe side effects from coronavirus vaccines. (Reporting by Bhanvi Satija in Bengaluru; Editing by Krishna Chandra Eluri)