A new descendant of the Delta variant of the coronavirus emerged in the United Kingdom in July, which virologists are now closely monitoring. This subvariant, AY.4.2., is also already observed in the Netherlands. The subvariant stood out in the UK because it now accounts for six percent of the infections there. Infection rates are also rising rapidly in the country.
The subvariant has been seen in several other countries. RIVM also picked him up in the germination surveillance in the Netherlands over the past ten weeks. One to two out of a thousand infections here are due to AY.4.2. That share is not yet increasing.
Too little is known about AY.4.2 to determine whether it will change the course of the pandemic. The key questions are: is it more contagious, is it more pathogenic, and will the vaccines protect against it?
Researchers at the British Sanger Institute estimate that this new offshoot of the virus family tree is 10 to 15 percent more infectious than Delta. That is why the mutant has already been christened ‘Delta-plus’. Other British genome researchers doubt whether the infectiousness is so elevated.
There is no indication whatsoever for the second question, whether AY.4.2 is more sickening, says virologist Marion Koopmans of Erasmus MC.
Two additional mutations
The third question, about the vaccines, is still open. The AY.4.2 subvariant has two additional mutations in the spike protein, the extension through which the virus enters our cells. Fortunately, those changes are not in the part of the spike protein that sticks to the receptor on human cells. “But one of the mutations, Y145H, is located in a place where antibodies bind, so it could be that this virus variant is less easy to neutralize,” says Koopmans. Whether the variant indeed escapes the defense is now being investigated.
The Groningen vaccinologist Anke Huckriede is not so concerned for the time being. “It is not yet clear to what extent the mutations affect the binding of antibodies, but it will probably not have direct consequences for the effectiveness of the vaccines.”
A small decrease in the binding of antibodies does not necessarily have major consequences. “The antibodies raised by the vaccines are about 10 percent less potent against Delta than against Alpha, but the vaccines still work well against Delta,” says Huckriede.
Thousands of different variants of the coronavirus are circulating worldwide. Four are classified by the WHO as a variant or concern, including Delta, which also includes all AY variants.
“I am particularly worried about the total increase in circulation,” says Koopmans. From December 2020, the Alpha variant supplanted previous variants of the virus. Alpha was 50 percent more contagious. Before the summer of 2021, the Delta variant, in turn about 60 percent more infectious, supplanted its predecessor Alfa. Koopmans: „But it is not what you want. It underlines that reduction remains important. If it spreads a little more easily, you’ll have to try a little more to restrict circulation.”
A version of this article also appeared in NRC Handelsblad of 23 October 2021
A version of this article also appeared in NRC in the morning of October 23, 2021
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