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XBB And BQ.1: Two New COVID-19 Variants With Hundreds Of Cases Already Reported In UK

They're much better than Omicron at evading immune responses.


Dr. Katie Spalding

Katie has a PhD in maths, specializing in the intersection of dynamical systems and number theory.

Freelance Writer

Artists impression of a covid particle on top of a stonks-like graph
oh god what now. Image Credit: ffikretow/Shutterstock

The presence of two new sublineages of COVID-19, designated as variants BQ.1 and XBB, have been confirmed in the UK, with more than 700 cases of BQ.1 and 18 of XBB being detected in the country recently. While neither sublineage is currently considered a variant of concern, experts have cautioned that they are likely highly immune resistant – and possibly even able to evade current vaccine immunity.

It’s been almost a year since a COVID-19 variant known as B.1.1.529 was officially designated a variant of concern, and renamed Omicron. Since then, this oddball variant has taken over the world: close to 100 percent of cases worldwide today are some form of the Omicron variant.


For now, at least, any cases of BQ.1 or XBB logged across the world are only adding to Omicron’s total. That’s because both sublineages are descendants of the Omicron variant: XBB is a recombinant of two previous Omicron sublineages, while BQ.1 is a subvariant of BA.5, the so-called “master of disguise” version of Omicron that was first recorded in South Africa in February and accounted for four-fifths of cases in the US by July.

With statistics like that, it’s not surprising that the two new variants have experts worrying – even if the actual case numbers are still fairly low.

“The biggest concern we’re seeing is that in early data these variants are starting to cause a slight increase in infections,” University of Warwick virologist Lawrence Young told The Independent

“In a way, this was to be expected but it does demonstrate that we’re not out of the woods yet at all with this virus, sadly,” he said.


Perhaps the biggest reason for this goes back to the mutation that made Omicron so successful in the first place: it’s much better than previous versions at evading immune responses. That means more frequent infections, and less protection from vaccines and previous infections – and that, in turn, means more opportunities for the variant to mutate further.

Most Omicron subvariants have inherited this same immunity-evading ability, and BQ.1 and XBB are no exceptions. While it’s still early days, initial evidence suggests that XBB is even better at reinfecting previously recovered or vaccinated individuals than previous Omicron variants, and it’s thought to be the variant driving the recent spike of COVID cases in Singapore, where nearly three out of every five XBB cases worldwide have been reported. 

Meanwhile, BQ.1 – on which director of the National Institute of Allergy and Infectious Diseases Anthony Fauci sounded the alarm earlier in the month – went from “virtually unheard of” to comprising one-tenth of all cases in the US in a matter of weeks. Its speed of spread seems to be unprecedented, even compared to previous record holder Omicron Original™, and early studies, although not yet peer-reviewed, suggest the new subvariant’s ability to evade antibodies is much stronger than its ancestor Omicron.

While all this may be concerning, what it isn’t is unexpected. Omicron’s ability to evade immune responses has led to what some researchers are calling “variant soup” – a seemingly chaotic and unending series of new sublineages emerging, rising to dominance, and then being beaten out by some other new contender. 


But because all these new lineages are so closely related to each other, it’s rarer than you might think that any becomes a variant of concern. Neither the World Health Organization (WHO) nor the UK’s Health Security Agency (UKHSA) have labeled either subvariant as such: “Based on currently available evidence, [we do] not feel that the overall phenotype of XBB* and BQ.1* diverge sufficiently from each other, or from other Omicron sublineages with additional immune escape mutations, in terms of the necessary public health response, to warrant the designation of a new variant of concern and assignment of a new label,” the WHO confirmed in a press release Thursday.

Nevertheless, both bodies are monitoring the situation closely – and despite both subvariants’ improved ability to evade immune defenses, it’s important to note that experts still advise using common-sense and long-standing COVID-19 protection measures.

“Vaccination remains our best defense against future COVID-19 waves, so it is still as important as ever that people come take up all the doses for which they are eligible as soon as possible,” said Meera Chand, Director of Clinical and Emerging Infection at UKHSA, in a statement released on Friday.

“It is not unexpected to see new variants of SARS-CoV-2 emerge,” she noted, “[and] neither BQ.1 nor XBB have been designated as variants of concern… UKHSA is monitoring the situation closely, as always.”


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