Los Angeles, Jan 28 (IANS): Omicron's new subvariant XBB.1.5 is estimated to account for over 60 per cent of the Covid-19 cases in the US for the week ending January 28, according to data released on Friday by the US Centers for Disease Control and Prevention (CDC).

XBB.1.5 is spreading quickly in the US. It made up 37.5 per cent of the total cases in the week ending January 14, and rose to 49.5 per cent in the week ending January 21, according to the CDC.

XBB.1.5 is currently the most transmissible variant in the country. The subvariant may spur more Covid-19 cases based on genetic characteristics and early growth rate estimates, according to the WHO.

Another two dominant Omicron subvariants BQ.1 and BQ.1.1 accounted for about 30 per cent of new Covid-19 cases in the US in the latest week, CDC data showed as quoted by Xinhua news agency report.

The CDC this week published the first estimate of the updated Covid-19 booster shot's efficacy against XBB.1.5, finding that the shots are at least 40 per cent effective against symptomatic illness from subvariants XBB.1.5 and XBB among fully vaccinated adults within three months of the shot's administration.