While the BQ.1 and BQ.1.1 COVID subvariants have gained traction across the U.S. in recent days, another new strain is responsible for a surge in cases in Singapore.
Referred to as the "nightmare" variant in some reports, XBB is the combination of two omicron subvariants - BA.2.10.1 and BA.2.10.75 - and is said to have a "significant growth advantage," said Dr. Maria Van Kerkhove, an infectious disease specialist and the technical lead for COVID-19 response at the World Health Organization.
Van Kerkhove explained data about the latest strain remains limited, but said the one study that was conducted with XBB shows "significant immune invasion." However, is it really any different than any of the other omicron strains that also appear to be more immune-invasive?
"We do know this recombinant has a significant growth advantage. All of the subvariants of omicron are showing increased transmissibility and properties of immune escape," Van Kerkhove said. "With this XBB recombinant we have one study based on a pseudo virus, so not a live virus, that is analyzing antibody escape and it's showing significant immune evasion. And this is of concern for us because we need to ensure that the vaccines that are in use worldwide will remain effective at preventing severe disease and death."
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In the U.S. specifically, BQ.1.1 and BQ.1 cases have climbed in recent weeks, with both surpassing other recent strains like BF.7 in their spread, according to the Centers for Disease Control and Prevention.
CDC data showed as of the week ending Oct. 22, BQ.1 made up 9.4% of recent cases, while BQ1.1 was said to be behind 7.2% of new cases. The numbers marked a notable increase from the week prior when each made up 5.7% of recent cases. BF.7 remained behind the other strains during both week-long periods, the data revealed. BF.7 accounted for 5.4% of cases the week ending Oct. 15 and 6.7% of cases for the week ending Oct. 22.
Van Kerkhove said there have been no signs of increased severity in the XBB, BQ.1.1 and BQ.1 variants, "but it's very early, and we have very little data to assess this."
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"We need to be prepared for this," the doctor said. "Countries need to be in a position to conduct surveillance, deal with increases in cases and perhaps deal with an increase in hospitalizations. We don't see a change in severity yet and our vaccines remain effective, but we have to remain vigilant."
Speaking during a Facebook live question-and-answer session earlier this week, Dr. Allison Arwady, commissioner of the Chicago Department of Public Health, explained that any of the subvariants that have recently circulated are related to omicron. Because XBB, BQ.1.1 and BQ.1 all have characteristics of omicron, the vaccine and treatments for the strain should be effective, at least to some degree.
If a variant without any relation to omicron were to emerge, that could be particularly troubling.
"So I am less worried about these little ones although I don't love the more rapid increase, and I'm more concerned if we start to see something, and then not only remember how we talked about Delta didn't help us," the doctor said.
Arwady has noted that seasonal shifts could play a role in the rise of new variants.
"The way COVID, like any other virus, mutates, creates new variants is by spreading," she previously said. "Every time there's a new COVID infection, there is an opportunity for the virus to mutate just a little bit in the genetics of it. And when we start to see more COVID infections happening, we also start to see more variants. That's just how it works. So the fact that we're heading into colder weather, it doesn't surprise me at all that we would see more mutations."
Dr. Anthony Fauci, White House chief medical advisor, said it does appear that the new bivalent COVID boosters, specifically formulated to combat omicron subvariants, are still effective at preventing serious illness and death even with the new variants that are emerging. However, he did note the data was preliminary.
Arwady agreed, encouraging people to take prevention measures with the possibility of a COVID surge this winter.
"We're not in quite as stable place as we were six weeks ago... but the best news is everything is still omicron," she said. "And so getting your fall 2022 vaccine should give us that extra protection we're going to need... remember that the updated variant is specifically good for the BA.4, BA.5, which is more than 80% of what we're seeing right now."
