Omicron subvariant XBB.1.5 continues to increase share of COVID-19 cases - CDC
undefined undefined/iStock via Getty Images

Cases of XBB.1.5, a subvariant of the COVID-19 Omicron variant, are continuing to grow, based on CDC data.
XBB.1.5 is considered the most transmissible and immune evasive subvariant so far detected.
CDC data posted on Friday found that for the week ending Jan. 7, XBB.1.5 has accounted for 27.6% of COVID infections. Related subvariant XBB accounted for another 4.9%. Omicron subvariants BQ.1 and BQ 1.1 still accounted for the majority of cases -- 34.4% and 21.4% of cases, respectively.
For the week ended Dec. 31, XBB.1.5 and XBB represented, respectively, 18.3% and 5.3% of infections.
Whether XBB.1.5 causes more severe disease is unclear.
In a Wednesday Twitter post, White House COVID-19 Response Coordinator Ashish Jha said that Pfizer's (NYSE:PFE) Paxlovid and Merck's (NYSE:MRK) molnupiravir, both antivirals, "should work fine based on what we know."
The US FDA on Friday also said it does not believe that AstraZeneca (NASDAQ:AZN) antibody cocktail Evusheld is effective against XBB.1.5, Bloomberg reported. In October, the agency warned healthcare providers that Evusheld may not be effective against Omicron subvariants.