What is Omixjon variant CH.1.1?

CH.1.1 belongs to the sixth generation sub-branch of Omixon variant BA.2.75. The latest research shows that the immune escape ability of CH.1.1 is increased due to the addition of multiple mutation sites. At the same time, a new mutation site (L452R) was once the characteristic mutation site of Delta mutant. However, it is worth noting that this mutation site also exists in many other sub-branches of Omixon variants, such as BA. 5.3 and BA. 5.1.3.

Since November 2022, the proportion of CH.1.1 in the epidemic strains of COVID-19 in the United States has increased. In the fourth week of 2023, the prevalence of CH.1.1 in the United States was the fifth, second only to XBB.1.5, BQ.1.1, BQ.1 and XBB variants.

CH.1.1 Will it be more pathogenic?

At present, there is no enhanced pathogenicity of CH.1.1 mutant, which still needs further attention. Generally, after the emergence of a new virus strain, the infection cases need to reach a certain scale and continue for a period of time before the pathogenicity of the new virus strain can be preliminarily determined.

CH.1.1 Global epidemic characteristics

According to the sequence included in the GISAID database, CH.1.1 was first discovered in India on July 8, 2022. In the past month, CH.1.1 and its sub-branches accounted for more than 6% of the global sequence number. As of January 30, 2023, it has been monitored in 67 countries or regions, mainly in the United Kingdom, Denmark, Singapore and other countries, accounting for about 25% of the COVID-19 sequences uploaded in the United Kingdom in the past month.

CH.1.1 Detection in China

On November 13, 2022, China detected the evolution branch of CH.1.1 from a Thai imported case sample (sampled on November 10, 2022) submitted by Tianjin for the first time through genome sequencing. As of January 30, 2023, a total of 24 imported cases of CH.1.1 and its sub-branches were detected. The source of imported cases involves 15 countries or regions. No local infection cases of CH.1.1 and its sub-branches were detected.

CH.1.1 Can it cause a second round of infection?

Although the immune escape ability and transmission advantages of the CH.1.1 mutant strain are further enhanced, leading to an increase in the risk of breakthrough infection and reinfection, high levels of neutralizing antibodies exist in most of the population in China, which has a certain cross-protection effect on CH.1.1, and CH.1.1 will not cause local large-scale epidemic in the short term. Vulnerable people (the elderly over 65 years old, patients with basic diseases and those without vaccination) and non-infected people still need to strengthen personal protection.

How to face CH.1.1?

Adhere to personal protection, maintain good hygiene habits