While the United States contends with the newly detected COVID omicron BQ.1 subvariants, another highly mutated strain of the coronavirus called XBB is tearing across Southeast Asia, where in some countries, it has caused the number of cases to double in a day.
Some more sensationalist reports have called XBB a “ nightmare variant ” due to its apparent ability to evade immunity and dampen some therapies. But infectious disease experts say it is too soon to jump to such broad conclusions.
“That is pretty irresponsible reporting because it’s impossible to know what all these variants mean,” said UC Berkeley infectious disease expert John Swartzberg.
“We are seeing a slew of new variants that are using a similar approach to survive — they are finding ways to evade the way we get immunity from vaccines and previous infection with changes on the spike protein,” he said.”XBB is no different from the others.”
The subvariant was first detected in August in India and has since been sequenced in more than 17 countries, including Bangladesh, Japan, and Singapore, where it has caused cases to spike at an alarming rate.
“XBB is now the predominant subvariant circulating in the community, accounting for 54% of local cases,” up from 22% the previous week, according to a bulletin from the Singapore Ministry of Health.
The subvariant has overtaken BA.5, which is estimated to account for 21% of cases in the country — with many of the new cases being reinfections.
“It will be their second biggest wave after BA.2 — even bigger than BA.5,” said Eric Topol, executive vice president of Scripps Research in San Diego.
But he added that Singapore’s 79% booster uptake rate and strict virus mitigation measures appear to be blunting the impact of the new strain when it comes to the worst outcomes of the disease.
“The number of people dying or in the ICU is really low,” he said. “Their protection level is really solid.”
Singapore’s health ministry added that so far “there is no evidence that XBB causes more severe illness.” Like BQ.1, there are indications that XBB is resistant to the monoclonal antibody treatments Evusheld and bebtelovimab, according to a pre-print study from researchers in China.
The good news is the updated bivalent boosters — which contain half the recipe that targeted the original coronavirus strain and half protection against the dominant BA.4 and BA.5 omicron versions — are designed to broaden immune defenses against newer strains. Experts just don’t know how much.
“We might expect some dent in efficacy,” Topol said.
BQ.1 and XBB — both descendants of the omicron BA.2 subvariant — appear to have similar growth advantages. But they are surging in different geographic regions, with the former mostly affecting North America, Europe and Africa while the latter has been detected in Asia.
In the few countries where they overlap, the two strains appear to be co-circulating rather than out-competing each other.
“If the immunity from the BQs is enough to not let us get sick from XBB then we could get some cross-protection there,” said Swartzberg. “What we can be doing in the meantime is getting immunized and being more assiduous, specifically by wearing masks indoors in crowded places.”
So far, 23 sequences from XBB have been detected in the US, including six cases in California, based on data from GISAID, an international research organization that tracks virus variants.
“XBB is a chimera,” Natalie Thornburg, the CDC’s lead respiratory virus immunology specialist, said during a webinar this week. “I think there have been a couple of sequences identified in the United States. But it’s way, way, way, way below that 1% threshold. I mean, it’s really like a handful of sequences.”
Topol said he is more concerned about the omicron coronavirus variant BQ.1 and its sibling BQ.1.1, which could drive another winter surge in the U.S. and could knock the BA.5 variant out of its dominant spot — especially with sluggish booster uptake.
“We’ve got another bad variant and we don’t have enough people protected,” Topol said. “We’re booster-vaccine deficient and we’re not in a good place to deal with a very tough variant like BQ.1.”
Nationally, about 14.8 million Americans have received the updated COVID-19 booster shots since they became available in early September, based on numbers reported by the Centers for Disease Control and Prevention. That’s a little under 7% of the more than 209 million vaccinated people who are eligible — in stark contrast to Singapore’s robust numbers.
“We’re going to have another wave,” Topol said. “The question is, how bad is it going to be?”
Aidin Vaziri is a San Francisco Chronicle staff writer. Email: avaziri@sfchronicle.com
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Is there really a COVID 'nightmare variant' spreading? Here's what experts say - San Francisco Chronicle
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