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XE was first discovered in the UK on February 15 this year.

Before XE, we need to learn some basic knowledge about COVID-19. The structure of COVID-19 is simple, that is, nucleic acids plus a protein shell outside. COVID-19 protein is divided into two parts: structure protein and non structural protein (NSP). Structural proteins are the four kinds of spike protein S, envelope protein E, membrane protein M and nucleocapsid protein N. They are the proteins necessary to form virus particles. For non structural proteins, there are more than a dozen. They are the proteins encoded by the virus genome and have certain functions in the process of virus replication, but do not bind to the virus particles. 

One of the most important target sequences for nucleic acid detection (RT-PCR) is the relatively conservative ORF1 a/b region of COVID-19. Mutations of several variants do not affect nucleic acid detection.

As RNA virus, COVID-19 is prone to mutation, but most of the mutations are meaningless. A few of them will have negative effects. Only a few mutations can enhance their infectious, pathogenic or immune escape ability.

The results of gene sequencing showed that the ORF1a of XE was more from Omicron’s BA.1, while the rest comes from Omicron’s BA.2, especially the genes of S protein part – which means that its transmission characteristics may be closer to BA.2.

BA.2 is the most infectious virus found in recent years. For the endogenous infectivity of a virus, we usually look at R0, that is, an infected person can infect several people without immunity and protection. The higher the R0, the greater the infectivity.

Early data showed that the growth rate of XE was higher than that of BA.2 increased by 10%, but later data showed that this estimate is not stable. At present, it can’t be determined that its higher growth rate is the advantage brought by restructuring.

It is preliminarily believed that the next major variants may be more infectious than the current BA.2 has more advantages, and it is difficult to accurately predict how its toxicity will change (increase or decrease). At present, the number of these new variants is not many. It is impossible to draw a conclusion whether any of them may develop into major variants. It needs further close observation. For ordinary people, there is no need to panic at present. Face these BA.2 or possibly recombinant variants, vaccination is still very critical.

In the face of BA with strong immune escape ability 2. In the case of standard vaccination (two doses), the effective rate of the two vaccines used in Hong Kong for the prevention of infection has been greatly reduced, but they still have a strong effect on the prevention of severe illness and death. After the third vaccination, the protection was comprehensively improved.