BA.2.75 (derived from Omicron 2) has all the credentials to supplant the current dominant BA.5, but its growth seems slower. Here’s what we can expect and what will happen with the updated vaccines
The new autumn Covid wave will be led by under variant Omicron BA.2.75 (nicknamed on social media “Centaur»)? Maybe yes. Here’s everything we know so far.
Diffusion (1 case in Italy)
BA.2.75 has all the credentials to be there number one candidate to replace the current dominant BA.5 and therefore “yes”, but it was already classified in May in India and, despite having arrived in several countries (India above all, USA, but also other 35 states) did not generate such massive waves of infections. 1 sequence was also recorded in Italy (as of 24 August from Pango, international genome collection site), where the predominant variant is BA.5.
In India as early as mid-August BA.2.75 had replaced BA.5, but (according to data collected by Fred Hutch researcher Trevor Bedford, visible in the graph below), despite this, there was no coincidental increase in total cases.
Growth forecast
This is because the Logistics growth rate of BA.2.75 seems lower compared to that initially seen for BA.5: initial estimates of Rt for BA.2.75 in the USA are at about 1.3 which is greater than the current Rt of BA.5 stopped at about 1.0, but lower than the initial Rt of BA.5 of about 1.6. What could it mean? In general, variants with a higher initial Rt are expected to cause larger outbreaks. BA.2.75 could replace BA.5, but relatively slowly, over the course of months, and in the meantime the hope is that it will cause modest epidemics, but that is not necessarily the case. The bad news is that is acquiring new spike mutations which could “reinforce” it. As written above, already on the “Centaurus” card she worries about yours high transmissibilitythe data must then be crossed in the various territories with the percentage of infected, with the chronology of the waves and the percentage of vaccinated in the various countries.
More efficient at binding to human receptors
In particular, one of the latest studies on the transmissibility of BA.2.75, is Italian, published in theEuropean Journal of Internal Medicine by the University of Insubria: shows the effect of mutations of the variant on human receptors, comparing it with that of Omicron 5. The results show that “Centaurus” is very efficient in binding to human ACE2 receptors (3,000 times better than the first Alfa variant), which makes it potentially able to spread and become predominant.
Features
BA.2.75 ha 8 mutations on the spike, 45 mutations in common with BA.5 and 15 peculiar ones. In particular, it differs appreciably from the ‘parent’ BA.2 with two key mutations: G446S and R493Q. G446Ssummarize the scientists of the Protein and Virus Evolution Laboratory of Fred Hutch (USA), is in one of the most powerful antibody escape sites induced by current vaccines.
Regarding the contagiousness it has been written about the ability to evade antibodies that we trained with a previous infection or the vaccine there is a study (not yet published) by Imperial College London, Karolinska Institutet in Stockholm, University of Cape Town and Polytechnic University of Zurich which says that However, the ability of BA.2.75 to escape our antibodies would not be better than those of Omicron 5.
The greater or lesser lethality, on the other hand, can only be measured in the field, in hospitals, and we still have no data on this. So far, however, the virus has not gone in the direction of increasing its pathogenic impact.
The updated vaccines
Regarding the fourth dose andefficacy of vaccines we can see that the capacity of SARS-CoV-2 to “mock” the antibodies of vaccines is increasing, also because the distance of the variants that have followed over time from the original Wuhan virus (on which the vaccines in use have been designed) it is abysmal, the stocks are a lot different from each other even within Omicron (as seen in this image above, taken from a study by Science modified by Eric Topol).
This is why the autumn campaign will be based on updated vaccines (as confirmed by al Health Courier the National Institute of Health by Graziano Onder (WHO his interview on Covid deaths in Italy).
There is a choice to be made by the European Medicines Agency (EMA): which vaccine to approve for the autumn campaign? Moderna based the updated vaccine on Wuhan and BA.1 (and the UK approved it). Pfizer, on the other hand, is a trivalent with Wuhan, BA.4 and BA.5 (but with final testing only on mice, for now). “Centaurus” comes from Omicron 2, but it’s probably better to deal with it with an up-to-date vaccine on any Omicron strain than the current ones based on a missing virus (which are still doing a very good job especially on preventing severe disease and deaths anyway).
August 26, 2022 (change August 26, 2022 | 13:51)
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