It’s a story perhaps more appropriate for Halloween than for the festive holiday season, given its scary implications.
Not too dire so far, until the researchers’ other findings are considered.
The BQ.1, BQ1.1, XBB, and XBB.1 subvariants are the most resistant to neutralizing antibodies, researcher Qian Wang, PhD, and colleagues wrote in a study published online in the journal Cell. This means people have no or “markedly reduced” protection against infection from these four strains, even if they’ve already had COVID-19 or are vaccinated and boosted multiple times, including with a bivalent vaccine.
On top of that, all available monoclonal antibody treatments are mostly or completely ineffective against these subvariants.
What does that mean for the immediate future? The findings are definitely “worrisome,” said Eric Topol, MD, founder and director of the Scripps Translational Research Institute in La Jolla, Calif.
But evidence from other countries, specifically Singapore and France, show that at least two of these variants turned out not to be as damaging as expected, likely because of high numbers of people vaccinated or who survived previous infections, he said.
Still, there is little to celebrate in the new findings, except that COVID-19 vaccinations and prior infections can still reduce the risk for serious outcomes such as hospitalization and death, the researchers wrote.
In fact, Centers for Disease Control and Prevention data released on Dec. 16 shows that people who have received four shots of the original COVID-19 vaccines as well as the bivalent booster were 57% less likely to visit an urgent care clinic or emergency room, regardless of age.
It comes at a time when BQ.1 and BQ.1.1 account for about 70% of the circulating variants, data show. In addition, hospitalizations are up 18% over the past 2 weeks and COVID-19 deaths are up 50% nationwide, The New York Times reported.
Globally, in many places, an “immunity wall” that has been built, Dr. Topol said. That may not be the case in the United States.
“The problem in the United States, making it harder to predict, is that we have a very low rate of recent boosters, in the past 6 months, especially in seniors,” he said. For example, only 36% of Americans aged 65 years and older, the group with highest risk, have received an updated bivalent booster.
An evolving virus
The subvariants are successfully replacing BA.5, which reigned as one of the most common Omicron variants over the past year. The latest CDC data show that BA.5 now accounts for only about 10% of the circulating virus. The researchers wrote: “This rapid replacement of virus strains is raising the specter of yet another wave of infections in the coming months.”
BQ.1 and BQ.1.1 evolved directly from BA.5 – adding more and some novel mutations to the SARS-CoV-2 virus. XBB and XBB.1 are the “offspring” of a combination of two other strains, known as BJ.1 and BA.2.75.
The story sounds familiar to the researchers. “The rapid rise of these subvariants and their extensive array of spike mutations are reminiscent of the appearance of the first Omicron variant last year, thus raising concerns that they may further compromise the efficacy of current COVID-19 vaccines and monoclonal antibody therapeutics,” they wrote. “We now report findings that indicate that such concerns are, sadly, justified, especially so for the XBB and XBB.1 subvariants.”
To figure out how effective existing antibodies could be against these newer subvariants, Dr. Wang and colleagues used blood samples from five groups of people. They tested serum from people who had three doses of the original COVID-19 vaccine, four doses of the original vaccine, those who received a bivalent booster, people who experienced a breakthrough infection with the BA.2 Omicron variant, and those who had a breakthrough with a BA.4 or BA.5 variant.
Adding the new subvariants to these serum samples revealed that the existing antibodies in the blood were ineffective at wiping out or neutralizing BQ.1, BQ.1.1, XBB, and XBB.1.
The BQ.1 subvariant was six times more resistant to antibodies than BA.5, its parent strain, and XBB.1 was 63 times more resistant compared with its predecessor, BA.2.
This shift in the ability of vaccines to stop the subvariants “is particularly concerning,” the researchers wrote.