This is the goal of immunity against the virus, both from vaccines and prior infection.
The spike protein is the part of the virus that it uses to attach to human cells, as well as the target of immunity against the virus from both vaccines and prior infection. BA.2 shares many of these mutations as the original Omicron variant, but also has 28 unique genetic mutations of its own. Four of these genetic changes are in the spike protein, which explains why some of its features differ from the original Omicron variant (ba.1), including the fact that it appears to be about 30 to 50% more infectious than ba.1. it happens. What is ‘recombinant’? Just as we have seen new forms of the virus emerge, followed by the evolution of subvariants or different lineages, the SARS-CoV-2 virus continues to mutate in other ways as well. In recent times we have seen not only spontaneous changes in the genetic code responsible for the changes described above, but also so-called recombinants.
A recombinant is one where related viruses exchange genetic material so that both can form new variants with genetic material from the original virus. It can arise when viruses from two different strains (or variants or subvariants) co-infect the same cell. The genetic material of the virus can mix to form a new recombinant virus, which has the properties of one or both of them of the original virus. So the properties of the recombinant virus depend on which parts of the genetic material from the original virus make up the new version – just as you might have a nose like your mother’s and eyes like your father’s. When delta and omicron recombine, the resulting progeny is referred to as a “deltachron” (though more officially these are referred to as xd and xf).
It has also been identified in India, China and Thailand.
This type of recombinant was first identified in France in mid-February and appears to have the genetic sequence mostly identical to that of delta, but with aspects of the spike protein from Omicron ba.1. So what is XE and where is it spreading? XE is a recombination of BA.1 and BA.2. There are many other ba.1 and ba.2 recombinants including XQ in the UK, XG from Denmark, XJ from Finland and XK from Belgium. XE although still comprises a small proportion of sequenced cases, has shown evidence of community transmission, at least within England, where it was first detected in mid-January. Only over 1,100 cases have been registered. It has also been identified in India, China and Thailand. Initially the pace of growth of XE did not appear to differ much from that of Ba.2, but recent data from the UK suggests that its growth rate is about 10 to 20% higher than that of Ba.2.
These figures are preliminary and based on small numbers, so may change as more information becomes available. If this is true, it means that Xe is likely to be slightly more infectious than Ba.2, Ba.2 was slightly more contagious than Ba.1, Ba.1 was more contagious than Delta. Do we need to worry? Our immune response that helps protect against COVID-19 is triggered by vaccination or previous infection, and it mostly targets the spike protein. Given that Xe has basically the same spike protein as Ba.2, it does not appear that our protection against Xe would be significantly reduced. The best way to slow the emergence of new variants as well as recombinants is to reduce the number of susceptible people, and to do so, cover as many people as possible under the protection of vaccination.