Q&A on the emerging Omicron variant CH.1.1

The CH.1.1 is a sixth generation subvariant of BA.2.75. Recent studies have shown that the immune escape ability of CH.1.1 is increased due to the addition of multiple mutation sites.

Since November 2022, the number of cases infected with CH.1.1 has been increasing in the US. By the fourth week of 2023, the prevalence of CH.1.1 in the US ranked fifth, following that of the XBB.1.5, BQ.1.1, BQ.1 and XBB variants.

 

There is no report about higher pathogenicity of CH.1.1 yet, or that it causes more hospitalizations or deaths. When a new virus strain appears, we are not able to tell if there is any change in its pathogenicity until it's been spread for a period of time and infected a certain amount of people.

 

According to the GISAID database, CH.1.1 was first discovered in India in July 2022. In the past month, CH.1.1 and its subvariants accounted for more than 6 percent of COVID samples sequenced around the world. As of January 30, 2023, CH.1.1 has been detected in 67 countries or regions, mainly in the UK, Denmark and Singapore. It is responsible for more than a quarter of infections in the UK.

 

As of January 30, 2023, the Chinese mainland had detected 24 imported cases infected with different sublineages of CH.1.1. The sources of imported cases come from 15 countries or regions. No locally transmitted CH.1.1 infections have been reported.

 

The neutralizing antibodies in the majority of the Chinese population is currently at a high level, which are protective against other variants, including CH.1.1.

The possibility of seeing another major outbreak caused by CH.1.1 at present is low. Particular attention should be paid to protecting the elderly and those with serious preexisting illnesses.