Mutations are being analyzed that make it appear even more contagious than BA.5 and more capable of overcoming the antibody barrier created by vaccines and previous infections. The virus keeps changing
Studies by epidemiologists and geneticists who follow SARS-CoV-2 are aimed at discovering and analyzing genome data stored globally (for example on GISAID, the international platform for collecting sequenced SARS-CoV-2 genomes) for individuate the next variant that could make you worry.
All the variants circulating in the world are now Omicron sub-lineages. In particular, after a few weeks of prevalence of BA.2, BA.5 is taking over (Also in Italywhere there is a prevalence of 60,71%
according to recent I-Co-Gen data).
These days, however, the eyes of scholars are focused on an underline that does not derive from BA.5, but from BA.2 and state classified as BA.2.75. this is a variant with the potential to worry and therefore to be monitored closely. Note that we are still talking about very few confirmed cases, one as of 4 July fortybut apart from a larger group in Indiathe geographic distribution is already international (with Australia, Canada, Germany, UK and New Zealand having deposited at least one sequence), which would rule out sequencing errors.
The analysis of the variant in question was made in detail by Tom Peacock, virologist of the Department of Infectious Disease at Imperial College London: BA.2.75 has 45 mutations in common with BA.5 and 15 peculiar ones. Between these, 8 mutations in the spike (BA.5 only has 3). In particular, it differs appreciably from the BA.2 parent with two key mutations: G446S e R493Q. G446S, synthesize the scientists of the Protein and Virus Evolution Laboratory of Fred Hutch (USA), in one of the most powerful antibody escape sites induced by current vaccines which still neutralize BA.2.
The forecast for BA.2.75 therefore one more greater ease of overcoming the antibody barrier created by vaccines or a recent Covid infection. However, G446S will have a minor effect on the antibodies of people with a previous infection produced by BA.1. Therefore, the antigenic advantage of BA.2.75 over BA.2 will be more pronounced in people who have not had exposure to BA.1.
The ability of SARS-CoV-2 to mock vaccine antibodies 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 were designed) is abysmal, the strains are very different from each other even within Omicron (as seen in this image above, taken from a study by Science
, modified by Eric Topol): this implies a greater difficulty in curbing infections, which means greater transmissibility of the virus and more people who get sick again. On the other hand, the protection that vaccines still offer against severe Covid disease remains solid.
The success of any variant also depends on the its intrinsic transmissibility: so far the infectious capacity of SARS-CoV-2 has always increased (making it one of the most contagious viruses ever to appear on the planet) and it could also do so with the variant BA.2.75 which has 8 mutations on the spike, but still a difficult variable to measure experimentally and it can be estimated only once there is sufficient epidemiological data to see how it is transmitted in the human population.
Nothing given to know, however, on the greater or lesser lethality, which is measured only in the field, in hospitals. So far, however, the virus has not gone in the direction of increasing its pathogenic impact and it is thought that this may be the case again.
In any case thesequence analysis remains essential to understand in which direction the coronavirus is moving and above all to plan timely interventions. It is also important to understand which variants and characteristics the vaccine updates
which risk chasing the succession of variants of SARS-CoV-2.
July 5, 2022 (change July 5, 2022 | 13:08)
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