The COVID-19 mutant is still evolving, and the "strongest immune escape ability" Omicron subtype virus strain XBB.1.5 has quickly become the number one epidemic strain in the United States.

According to reports, the latest data released by the US Centers for Disease Control and Prevention (CDC) show that XBB.1.5 accounts for 41% of COVID-19 cases in the United States this week, replacing the dominant position of BQ.1.1 and BQ.1.

It is worth mentioning that XBB.1.5 has risen rapidly in the past week, and the rate of infection has almost doubled. In the week ended December 24, the rate of XBB.1.5 infection was 21.7%.

At first, the XBB mutant was first discovered in India in August, then spread rapidly and soon became a major epidemic strain in Singapore, Malaysia and other countries. Since then, XBB mutants gradually evolved into Omicron sub-branches, including XBB.1 and XBB.1.5.

Studies have pointed out that the pathogenicity of XBB is not significantly enhanced, but because the mutation of the strain can better bind to human cell receptors, the immune escape ability of XBB.1.5 is higher. In addition, new crown neutralizing antibodies such as Zaiyuan and Eli Lilly and Co have been completely ineffective against XBB, and the efficacy of strengthening needles has been reduced, but small molecular drugs targeting conservative targets have maintained their efficacy.

XBB can better combine with cells and have stronger escape ability.

The latest research shows that the pathogenicity of XBB.1.5 is not significantly enhanced, similar to or lower than BA.2.75. However, its key mutation F486P can better bind to human cells and is more likely to infect humans.

Andrew Pekosz, a virologist at Johns Hopkins University, said that unlike other Omicron mutants, XBB.1.5 has an additional mutation, F486P, which has a stronger affinity to the human ACE2 receptor, binds better to cells and is easier to enter the human body.

Data posted on Twitter by Cao Yunlong, a biomedical researcher at Peking University, show that XBB.1.5 can not only escape antibody protection as effectively as a variant of XBB.1, but also has a high ability of immune escape and is better at binding to cells through key receptors.

Strengthening the protective efficacy of needles and reducing the small molecular drugs targeting conservative targets are still effective.

In a study published earlier this month in CELL, scientists at Columbia University warned that the increase in subvariants such as XBB could further undermine the protective efficacy of the current COVID-19 vaccine, leading to a surge in breakthrough infections and reinfections.

The results showed that in the case of at least two doses of mRNA vaccine, breaking through infection of BF.7 could not induce high levels of neutralizing antibodies to XBB.1 and XBB.1.5, and it was difficult to prevent reinfection. XBB subvariants are more effective than BQ subvariants in avoiding the protection of strengthening needles, and these two subvariants are by far the strongest variants in terms of vaccine protection.

According to the data in the journal NEJM, neutralizing antibodies (AstraZeneca PLC, GlaxoSmithKline PLC / Vir, Eli Lilly and Co, Shengyuan) listed in the United States have been completely ineffective against BQ.1.1 and XBB, only the small molecular drugs targeting conservative targets, such as Redsivir (Gilead), Naimatevir (Pfizer Inc) and Monoravir (Merck & Co Inc), remain effective.

Earlier, Fauci, the chief medical adviser to the Biden government, had said that the XBB subtype might reduce the protection of enhanced needles. Fauci said that the number of XBB infections in Singapore has increased significantly, but the number of hospitalizations has not increased at the same rate. The combination of XBB.1.5 and holiday travel may lead to an increase in cases in the United States, but intensive needles seem to be more effective in preventing severe cases.

XBB mutants have been detected in China, but have not yet formed dominant transmission.

At present, XBB.1.5 strains have been detected in Shanghai, and most of these cases are imported from abroad, which are under closed-loop and separate management, so it does not cause local large-scale transmission of BQ.1 family and XBB family.

China Disease Control previously pointed out that the branches of Omicron BQ.1 and XBB have been introduced into China, and their transmission advantages will gradually increase.

According to Xu Wenbo, director of the Institute of viral Diseases of the Chinese Center for Disease Control and Prevention, BF.7, BQ.1 and XBB have been detected in China in the past three months. A total of more than 130 sub-branches of O'Micron have been imported into our country, and these 50 sub-branches have caused related local cases or outbreaks, including BQ.1 and XBB. BQ.1 and its sub-branches were detected in 49 cases in 9 provinces. XBB subbranch was detected in 11 cases in 3 provinces. The whole BQ.1 and XBB have not formed dominant propagation in China (mainly BA.5.2 and BF.7 at present), but their transmission advantages will increase gradually, and may form a common cycle with BA.5.2 and BF.7, as well as other subbranches of more than 50 inputs.