BA.4 and BA.5 contagious Omicron variants

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The omicron sub-variant BA.5 is now also predominant in Austria. It is more contagious than the previously dominant variants. This is probably one reason infection numbers are not falling as in the past two summers.

However, the European Union health agency ECDC sees no evidence that BA.5 leads to a more severe disease course in covid-19 compared to previous omicron lines. The same is true for the BA.4 subvariant, but there are indications that the two subvariants may again infect more lung cells and thus cause more severe courses. This is due to mutations at critical sites in the spike protein, which are already known from the delta variant. However, it is not yet certain.

On May 12, 2022, the EU health agency ECDC classified the two subvariants BA.4 and BA.5 as variants of concern (VOC). They were discovered in South Africa at the beginning of the year, where they quickly became dominant and triggered a sharp rise in new infections by mid-May. In the meantime, however, the numbers there have dropped significantly again. In Europe, Omicron BA.5 first spread in Portugal. There, however, unlike in South Africa, not only did the number of infections rise significantly but so did the number of hospital patients and Covid-19-related mortality.

BA.4 and BA.5 are subvariants of the variant Omicron of the coronavirus SARS-CoV-2. Within a short time, Omicron could displace the variant Delta, which was predominant in most European countries until the end of 2021, because it is significantly more contagious. More precisely, the Omicron sub-variant BA.1 initially prevailed but was replaced within a few weeks by the even more contagious sub-variant BA.2. In recent months, scientists have identified other Omicron subvariants such as BA.4, BA.5, and others that are even more infectious than BA.2. These are even better able to circumvent the immune protection offered by vaccination, a previous coronavirus infection, or a combination of both than Omicron BA.1 and BA.2. This means that even those who were infected with one of these two subvariants only some time ago can become infected again with BA.4 or BA.5. This is presumably caused by mutations in the spike protein of the virus, which it uses to dock onto human cells.

Incidentally, the omicron subvariants BA.1 to BA.5 did not evolve one from the other, but all have a common origin from which they evolved separately.

It is impossible to tell what the future holds from the circulating variants. In the fall, when temperatures drop and infection numbers are expected to rise significantly again, other subvariants of Omicron or completely different, as yet unknown virus variants may have already spread.

But even variants like Delta, which appear to have disappeared, may survive unnoticed until then. This has been shown, for example, by wastewater studies in Israel. It is, therefore, possible that a variant that is more pathogenic and infectious than the currently predominant variant Omikron BA.2 will prevail in the fall.

However, it is equally possible that the coronavirus will not become more dangerous and that little or no infection control measures will be necessary for the fall and winter because many people in Austria are now protected from a severe covid 19 course by vaccination, a previous infection, or both. Vaccines adapted to the initially disseminated omicron subvariants are also expected to be available by the fall. However, these must then show whether they have advantages over the previous vaccines, for example, whether they effectively protect against infection.