The scenario of a new, more dangerous Sars-CoV-2 variant as an omicron has become a bit more realistic with a recent advance publication by scientists from the Pasteur Institute in Paris.

"XD", a genetic combination of Delta, the more virulent predecessor variant, and Omicron first appeared in southern France in mid-January.

It has meanwhile also been found occasionally in Germany, Belgium and the Netherlands and is characterized not only by genetic peculiarities, but it is also apparently clinically conspicuous: The researchers report that the loss of smell and taste is two to three times as frequent.

Joachim Müller-Jung

Editor in the feuilleton, responsible for the "Nature and Science" department.

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That's not a lot of clinical information.

But for a discovery that was not even three months old and for a variant that is obviously not spreading at breakneck speed, not much more can be expected.

Omicron, the currently dominant variant, which is known for its extremely easy transmission and the ability to evade the immune system and to repeat infections, finally became established more than half a year after its discovery.

This was the omicron subtype BA.1.

Probably almost simultaneously, another omicron subtype, BA.2, arose about a year ago.

And from these, in turn, further virus lines with slightly different mutations have developed.

The sister variant BA.2, which has some special mutations, has finally asserted itself against the prevailing corona viruses in the current, second omicron wave and is now on the way to becoming the dominant virus variant almost everywhere in the world, as it has already done in Germany or the USA to become.

Immunologically, the two omicron subtypes are very similar. As far as the effect of the vaccination is concerned, there are no major new fears based on the previous immunological laboratory tests.

What is the use of the fourth vaccination?

At the moment, however, none of the virus experts can say how things will turn out with virus recombinants such as XD.

The uncertainty is great, because parallel to XD, genetically different new combinations of delta and omicron and their subtypes, some with completely new mutations, have now been registered in the international virus gene databases such as GISAID and the "Pango Network": XS in the USA, XG and XH in Denmark, XQ in Great Britain, XK in Belgium and XM in turn in the Netherlands and Germany.

All in all, at least 80 individual clusters with omicron or delta recombinants are known, but almost all of their threat potential for humans is still unknown.

With a third vaccination dose or a double vaccination and an additional virus infection, the protection against serious illness is very high compared to both BA.1 and BA.2.

And for older people over the age of sixty, an Israeli study with more than 1.2 million Biontech vaccinated people has shown that the fourth dose only offers protection against infection for a few days to weeks, but four times higher and significantly longer-lasting protection against severe Covid -19

What this immunological protection against the previously successful omicron variants is still worth should one of the new recombinants or subsubtypes spread, but this remains completely unanswered.

The only thing that is clear is that the astonishingly rapid evolution of the virus is not stopping, it is not slowing down, especially in the current high-incidence phase.

The hope is that the current vaccines offer enough cross-immunity to at least be able to keep the wave of diseases small in autumn.

The vaccination rate in the population has become one of the key indicators for the further course of the pandemic.

And this importance is likely to increase rather than decrease.

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