Ssince the start of the COVID-19 pandemic, health officials have warned that the biggest obstacle to controlling the virus will be its ability to mutate into increasingly infectious and dangerous forms.
The latest release to cause concern is an emerging sub-variant of Omicron called BA.2.75.2. It has already acquired the ability to evade the immunity provided by current vaccines and cannot be neutralized by many of the available antiviral drugs. So far the tension has been reported in 47 countries and in 39 US states, where it still accounts for less than 1% of COVID-19 cases.
Here’s what we know so far about BA.2.75.2.
Where does BA.2.75.2 come from?
The BA.2.75.2, as its nomenclature suggests, is derived from the BA.2.75 subvariant. It is growing rapidly, especially in India, although BA.2.75.2 accounts for only 0.5% of cases worldwide so far. Because it shares many similarities with the existing subvariant, the World Health Organization did not identify BA.2.75.2 as a new variant, but listed it as a “subvariant of Omicron under surveillance,” meaning health officials should prioritize tracking cases to hopefully prevent spikes in infections. Some experts informally began to call it Centaur, after a A Twitter user gave him this nickname.
Why does BA.2.75.2 concern public health officials?
BA.2.75.2 picked up three additional mutations from BA.2.75, two of which are where the virus binds to human cells to infect them.
According to one study by Swedish researchers, published on September 16 as a preprint – meaning the study has not yet been peer-reviewed – these aberrations help BA.2.75.2 evade all currently available antibody treatments approved by the US Food and Drug Administration. except for one: bebtelovimab. Made by Lilly, this monoclonal antibody treatment is given as an intravenous infusion to people with mild to moderate symptoms of COVID-19 who are at high risk of progressing to more severe disease. But because the drug only targets a specific part of the virus’s spike protein, there’s no guarantee that the virus won’t also evolve mutations to avoid it.
On September 7 in New England Journal of MedicineJapanese scientists reported somewhat more encouraging findings in their tests of BA.2.75 versus available treatments. They also found that bebtelovimab could neutralize the variant, and also reported that some of the first antiviral treatments developed—remdesivir and molnupiravir—as well as the newest, Paxlovidalso remain effective.
But persistence is a feature of BA.2.75.2, which is why health officials are concerned. The Swedish scientists also reported that antibody levels against the virus in blood donors, some of whom had been vaccinated or recently infected with SARS-CoV-2, were five times lower against BA.2.75.2 than against the currently dominant Omicron variant , BA.5. They also found that BA.2.75.2 was resistant to the antiviral combination therapy Evusheld. Taken together, the scientists concluded, this variant “effectively avoids the draft [antibody] immunity in the population” and “represent[s] the most persistent variant characterized to date.”
How well do BA.2.75.2 vaccines work?
The picture is currently incomplete. Human studies of the latest COVID-19 booster vaccine— which target two other Omicron sub-variants, BA.4 and BA.5 — are not yet complete, and it’s unclear how effective they will be against BA.2.75.2 as well. But there are hints from studies involving the original vaccine about what protection people can expect if the variant becomes more widely available.
David Montefiori, a viral immunologist at Duke University Medical Center who oversees testing of the effectiveness of Moderna’s mRNA vaccine against new variants, is now studying how blood samples from people immunized with Moderna’s vaccine stack up against BA.2.75.2. In earlier studies against BA.2.75, the results were encouraging. IN correspondence published in New England Journal of Medicine on Sept. 9, he and his team reported that while antibody levels against the BA.2.75 virus were more than four times lower than levels against the original virus among people vaccinated with Moderna’s vaccine, they remained effective. However, the three additional mutations of BA.2.75.2 “could potentially make the virus less susceptible to neutralization,” he says, “but we need to test it and find out.” Results from these ongoing trials, funded by both Moderna and the National Institutes of Health, are expected in October.
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