The prestigious scientific journal Nature returns to take stock of the last two sub-variants of Omicron, BA.4 and BA.5 because, as the long in-depth analysis says in the attack, “Omicron is back“. The last two strains are feeding one resumption of infections in many countries of the world: they are much more contagious, more than BA.2 protagonist of the curve at the beginning of the year. But they seem to cause fewer hospitalizations of the previous “cousins” as well as seem to show off a lower lethality rate, elements obviously also linked to the widespread protection given by vaccines and previous infections, at least compared to the severe syndrome.
BA.4 and BA.5, more closely related to Omicron 2 – as some studies show, also pointing out how many genomes initially categorized as BA.2 were actually already attributable to BA.4 or BA.5 – which to Omicron 1, show mutations such as those called L452R and F486V in the Spike protein: they can grant the virus a search ability to dodge the immune responseespecially that of vaccination-induced antibodies, allowing it to bind better and better to host cell receptors.
Their role in fueling this summer (or winter in the northern hemisphere) wave seems to be based on their ability to infect people protected by previous forms of Omicron and other variants. Experts explain that, given the almost total removal of all containment measures (excluding some Asian countries, including the Chinese giant), the rise and inevitable fall of Omicron 4 and 5 will be linked to theimmunity of the population. It will only go down when a sufficient slice of the audience has been infected and, therefore, will be protected, slowing down the circulation of the virus. Likewise it will vary the impact on society and health systems: in South Africa, for example, a study explains that the latest wave produced a similar hospitalization rate to that of the beginning of the year, with a slightly lower lethality threshold. Both waves were also much softer than that caused by Delta. In Portugal, another country that has experienced the spread of the two sub-variants well ahead of the rest of Europe, the impact seems to have been similar, even in deaths, to that of the first Omicrons but not remotely comparable to that of the previous waves. . The difference, of course, depends on the demographic structure of the two countries: Portugal has a much older population than South Africa.
Much depends on the type of immunity that the population of a certain country has developed. In South Africa, for example, it is mixed: if it is true that only 5% received the booster and almost half finished the cycle in double dose, the very high rates of contagion recorded in the previous waves would have produced an effective hybrid immunity that offers high protection against severe disease, especially in older individuals. Indeed, the antibodies triggered by vaccination would appear less effective in contrasting the last two sub-variants, here is the reason for one very significant share of reinfections and mild syndromes. And even hybrid immunity (vaccination plus Omicron BA.1 infection) just doesn’t seem like a foolproof shield.
How will it proceed in the coming months? Hard to say. The emergence of new sub-variants, perhaps with one almost seasonal-half-yearly cyclicality as some investigations underline, it will continue. And with them the protection gained with vaccines and infections, especially against contagion and mild forms, will weaken by accumulating holes upon holes. «Nobody can say that BA.4 / 5 is the final variant. It is highly probable that further variants of Omicron will emerge, ”he explains Kei Sato, a virologist at the University of Tokyo. Researchers have identified several spots on the Spike protein that are currently recognized by antibodies that are activated by vaccination and previous infections, but which could mutate in future strains of Omicron. Much will also depend on the next phase of the vaccination campaignwhich should be based on products engineered not only from the Wuhan native strain but also from the Omicron 1 variant.
Another possibility is that a variant emerges from a completely different branch of the Sars-CoV-2 family tree from what led to the Omicron family, which among other things, according to experts, would be the daughter of patient-reservoirs within which the virus has had the opportunity to replicate for a long time and accumulate many mutations and deletions. Repeated infections of Omicron could create widespread immunity against subsequent lineages, uncovering the side of a completely different variant capable of overcoming people’s immune responses even more profoundly. Also the trend of less pathogenicity it could stop: the fact that viruses evolve towards less virulence is a myth. What could be consolidated, thanks to widespread immunity, is perhaps a slowdown in the emergence of worrying variants, at least in the medium term. On all this, another great unknown remains: the long Covidits consequences and the ability of these variants to trigger pathologies lasting months that can affect public health in a slower and more subtle way.
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Source: Vanity Fair