In a new study published in the scientific journal Cell, researchers from Columbia University and the University of Michigan warned that the Omicron subvariants BQ.1, BQ.1.1, XBB, and XBB.1 were “the most resistant [COVID] variants to date.”

The research team looked into how the new strains responded to antibodies by mixing them with blood samples from individuals who had either been immunized with three or four doses of the original vaccines, been given a new bivalent booster, or had postvaccination breakthrough infections caused by the BA.2 or BA.5 Omicron subvariants.

Their findings showed that the neutralization of BQ.1, BQ.1.1, XBB, and XBB.1 was “markedly impaired”—even when antibodies derived from the new bivalent vaccines were used.  

However, the updated vaccines did provide slightly better protection than the original vaccines, the study found.

The new so-called bivalent vaccines, which were designed by Pfizer and Moderna to work against both the original strain of COVID-19 and the more recent Omicron subvariants, were approved for use in the U.S. in August.

In participants who had been boosted with a bivalent vaccine, antibodies were 24 times lower against BQ.1, 41 times lower against BQ.1.1, 66 times lower against XBB, and 85 times lower against XBB.1 compared with their response level against the original strain of COVID that emerged in the Chinese city of Wuhan at the end of 2019.

The researchers also found that all clinical monoclonal antibodies—man-made antibodies used in pharmaceutical treatments for COVID like AstraZeneca’s Evusheld and bebtelovimab—were “rendered inactive against these variants.”

Drugs like these are typically used in immunocompromised patients to limit the virus’s spread inside their bodies after a positive test.

“Our findings indicate that BQ and XBB subvariants present serious threats to current COVID-19 vaccines, render inactive all authorized antibodies, and may have gained dominance in the population because of their advantage in evading antibodies,” the study’s authors wrote in their paper.

“Unfortunately, both BQ and XBB sublineages are now completely resistant to bebtelovimab, leaving us with no authorized antibody for treatment use. In addition…Evusheld is also completely inactive against the new subvariants. This poses a serious problem for millions of immunocompromised individuals who do not respond robustly to COVID-19 vaccines. The urgent need to develop active monoclonal antibodies for clinical use is obvious.”

Data from the Centers for Disease Control and Prevention shows that as of Dec. 10, BQ.1 and BQ.1.1 were, by far, the dominant strains of COVID in the U.S., accounting for a combined 68% of cases.

Back in October, as the BQ variants were gaining ground, White House chief medical adviser Dr. Anthony Fauci dubbed them “troublesome” because of the speed at which they were spreading.

XBB, meanwhile, accounted for 4.7% of cases in the week ended Dec. 10, making it the fifth most common subvariant in the United States. BA.5 and BF.7 rounded out the top five, coming in as the third and fourth most prominent subvariants, respectively.

Rising COVID cases prompt U.S. action

U.S. cases of COVID have risen drastically in recent weeks, with the number of people reporting positive tests rising 49.6% in the week ended Dec. 7 from the week before. The rise in cases, as well as an expected increase in infections over the coming winter months, has prompted the Biden administration to introduce measures including offering more free COVID tests and opening up more mobile vaccination sites.

In New York, health officials have advised the public to wear masks indoors and in crowded outdoor settings, as New York City faces rising rates of COVID-19 as well as flu and RSV.

The study published this week adds to existing concerns about the BQ and XBB subvariants’ ability to evade immunity and pharmaceutical interventions.

Scientists at Peking University’s Biomedical Pioneering Innovation Center in China found earlier this year that both variants escape immunity from bebtelovimab and Evusheld—and the authors also warned that both strains could potentially lead to more severe symptoms.