Covid, as is the new variant AY.4.2: perhaps more transmissible but less symptomatic

There is a variant of the Delta that UK genomic tracking systems monitor and to which, at the moment, they attribute the 12% of total new infections per day. Is called AY.4.2 and is a sub-variant of one of Delta’s two main lineages, improperly called by some Delta Plus. Identified for the first time last July, it took on the official name of VUI-21OCT-01. Apparently from the ongoing study React-1 of Imperial College London this sub-lineage would seem to trigger far less symptomatic syndromes than the Delta variant. But, on the other hand, it seems a little more contagious. Almost an adjustment of the variant currently largely dominant all over the world, with the exception of South America where variants such as Beta, Gamma and Mu remain present with slightly higher percentages. In Italy, the presence is still witnessed in a few dozen cases.

The survey released on November 18 explains that only a third of the tested cases infected with AY.4.2 developed the classic symptoms of Covid-19. With the strains of the AY.4 sub-lineage (the most common of Delta which gave rise to AY.4.1 and AY.4.2) this happens once in two. Two thirds, on the other hand, experienced symptoms of some kind, therefore not the full range of ailments, which instead happens in three quarters of those infected with Delta. In short, it would actually seem less aggressive or rather symptomatic.

On the other hand, the study also seems to confirm that the new variant could be slightly more transmissible, and therefore to be able to progressively supplant the Delta parent, but in fact it does not seem to lead to more severe Covid-19 nor to be able to evade the protection of vaccines, partial for contagion and very high for hospitalizations and deaths. At least no more than Delta can. According to the researchers, the minor symptomatology is linked to a negative and a positive aspect: if it is true that asymptomatic people, not knowing they are infected, will not isolate themselves, it is equally true that fewer symptoms mean less chance, for example through coughing, to transmit a high amount of viral particles to others. Some experts such as Jeffrey Barrett, director of the Covid-19 Genomics Initiative at the Wellcome Sanger Institute in Cambridge, and Francois Balloux, director of the University College London Genetics Institute, had suggested a higher transmissibility of 10-15%. But these are fragile numbers at the moment.

Since September, the growth of the variant has been 2.8% but according to the work of the Imperial College and the UK Health Security Agency, the third dose of vaccine – on which all countries are accelerating – it would seem it would reduce the risk of infection compared to both variants by 66% of those who were given two doses. The two mutations of greatest interest of the sub-variant, which overall has three, are always on the spike protein with which the virus binds to human cells: it is Y145H e A222V, already identified in various other lineages of Sars-CoV-2. Mutations can obviously cause vaccine resistance. However, it should be remembered that there is no evidence that the AY.4.2 variant is resistant to currently available vaccines. However, vaccinations are fundamental: more people get vaccinated, the fewer mutations occur, the less likely it is that a vaccine-resistant variant will emerge.

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