Discovered in South Africa, they are still not very widespread, but the WHO has included them in the list of those under observation. They have Omicron 2’s spike and other mutations that set them apart from all others. For now, no repercussions on the progress of cases or hospitalizations
The World Health Organization (WHO) has started monitoring two new ones sub-variants of Omicronidentified for brevity with the initials BA.4 to BA.5.
Sufficient signals to activate monitoring
The two variants were first sequenced in South Africa already in January and February and for the moment they have a very limited diffusion, but in recent days they have also been included in the monitoring of the UK Health Security Agency and ECDC (European Center for Disease Prevention and Control) because – we read in the English report dated 8 April – although the number of total genomes is small, the apparent geographical spread suggests that the variant is broadcasting successfully. For these variants, there is evidence of genomic, epidemiological or in vitro properties that might imply a significant impact on transmissibility, severity and / or immunity; realistically they could have an impact on the epidemiological situation in the European Union or the European Economic Area. However, the evidence is still preliminary or associated with great uncertainty, concludes the ECDC report note.
The (limited) diffusion
BA.4 and BA.5 have been reported so far in South Africa, Botswana, Belgium, Germany, Denmark and the United Kingdom.
The English report dates to January 10 the first sample of BA.4 in GISAID (the international SARS-CoV-2 genome sharing portal) from South Africa. Countries reporting BA.4 genomes via GISAID now include South Africa (41 genomes), Denmark (3), Botswana (2), and England and Scotland, which each report one.
Per BA.5 27 reported sequences are deposited, all from South Africa. This lineage shows samples taken from February 25.
The known characteristics
Professor Tulio de Oliveria, of the University of KwaZulu-Natal, director at the Center for Epidemic Response & Innovation (CERI) of South Africa, which helped the world discover Omicron, describes mutations which characterize the two sub-variants (which are not recombinant like XE, of which we have spoken WHO
).
BA.4 and BA.5 share una spike (the protein that attaches to human cells) simile a BA.2 (the strain also called Omicron 2 which is now the prevailing one in the world) with the exception of further mutations: 69-70del, L452R, F486V. This could mean one diffusion capacity of the virus (through the spike) similar to that of BA.2 which is very contagious, so much so that it has prolonged the tail of the waves of Omicron 1 (BA.1) in several countries.
BA.4 and BA.5 tra loro they differ in 3 mutations of amino acids outside the spike.
The good news that BA.4 and BA.5 (like BA.1) have the feature called deletion of the S gene (i.e. they are S negative) which allows i molecular buffers to locate them without the need for sequencing (which will have to be done later for confirmation). This will allow a more precise monitoring of the diffusion of the two variants.
Eyes on another mutation instead, la F486Vwhich could lead to greater leakage of antibodies compared to vaccines.
No alarm but rethink vaccines
For now, however, all hypotheses have to be confirmed and the data from the areas that sent the reports do not cause concern: in South Africa, despite the increase in the percentage of BA.4 and BA.5 genomes, there is no significant peak in infections and also hospitalizations and deaths, despite being winter, are at an all-time low. Many people infected with BA.1 and BA.2 probably enjoy one some protection also against BA.4 and BA.5.
The consideration made by specialists, however, that the continuous evolution of Omicron compared to current vaccines underlines the need for a updating of vaccines in use.
April 12, 2022 (change April 12, 2022 | 19:15)
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