BQ, XBB Omicron subvariants pose a critical menace to boosters

Evusheld injection, a new COVID treatment people can take before they become symptomatic, on Friday February 4, 2022 in Chicago.

Chris Sweda | Tribune News Service | Getty Images

The Omicron subvariants that have become dominant in recent months pose a serious threat to the effectiveness of the new boosters, render antibody treatments ineffective and could cause a rise in breakthrough infections, according to a new study.

Omicron subvariants BQ.1, BQ.1.1, XBB, and XBB.1 are the most immune-avoidable variants of Covid-19 to date, according to scientists at Columbia University and the University of Michigan. These variants combined currently cause 72% of new infections in the United States, according to data from the Centers for Disease Control and Prevention.

The scientists noted in a study published online Tuesday in the journal Cell that these subvariants are “hardly susceptible to neutralization” by the vaccines, including the new Omicron boosters. Also, the immune response of people vaccinated with earlier Omicron variants who had breakthrough infections was weaker than the subvariants.

“Taken together, our results suggest that BQ and XBB subvariants pose a serious threat to current COVID-19 vaccines, render all approved antibodies inactive and may have gained population dominance due to their advantage in antibody evasion.” , the scientists wrote.

Although these subvariants are more likely to cause breakthrough infections, the vaccines have been shown to be effective in preventing Omicron-related hospitalizations and serious illness, the scientists wrote.

The study looked at blood samples from people who received three or four shots of the original vaccines, people who received the new Omicron booster shots after three shots of the original vaccines, and people who were vaccinated with the original vaccines and also had breakthrough infections caused by BA.2 or BA.5 subvariants.

In people who received the omicron boosters, antibodies that block infection were 24-fold lower against BQ.1, 41-fold lower against BQ.1.1, 66-fold lower against XBB, and 85-fold lower against XBB. 1 compared to their performance against the Ancestral Tribe which emerged in 2019 in Wuhan, China.

However, according to the study, people who received the Omicron boosters had slightly higher antibody levels against all of these subvariants compared to people who received three or four shots of the original vaccines.

People who were vaccinated and had breakthrough infections had the highest antibody levels of any group in the study, although neutralization was also much lower against the subvariants than the ancestor strain.

The subvariants have evolved dramatically from earlier versions of omicron. BQ.1.1, for example, is about as different from omicron BA.5 as the latter subvariant is from the ancestral Covid strain, according to the study.

“Therefore, it is alarming that these newly emerging subvariants could further impair the effectiveness of current COVID-19 vaccines and lead to a surge in breakthrough infections as well as reinfections,” the scientists wrote.

However, XBB.1 poses the greatest challenge. According to the study, it is about 49 times more resistant to antibody neutralization than the BA.5 subvariant. Fortunately, XBB.1 currently causes no more than 1% of infections in the US, according to CDC data.

BQ.1.1 and BQ.1 account for 37% and 31% of new infections, respectively, while XBB causes 4.7% of new infections, according to CDC data.

Antibodies ineffective

According to the study, the main antibody drugs Evusheld and Bebtelovimab were “completely inactive” against the new subvariants. These antibodies are mainly used by people with weak immune systems.

Evusheld is an antibody cocktail used to prevent Covid in people with weak immune systems who don’t respond strongly to the vaccines. Bebtelovimab is used to prevent Covid from progressing to serious illness in organ transplant patients and others who cannot receive other treatments.

“This poses a serious problem for millions of immunocompromised individuals who do not respond robustly to COVID-19 vaccines,” the scientists wrote. “The urgent need to develop active monoclonal antibodies for clinical use is evident.”

The Food and Drug Administration has already withdrawn approval of bebtelovimab nationwide because it is no longer effective against the dominant Omicron variants in the US. Evusheld remains approved as the only option for pre-exposure prophylaxis.

New Covid infections rose about 50% to 459,000 in the week ended December 7, according to CDC data. The number of deaths from Covid rose by 61% to nearly 3,000 in the same week. Hospital admissions have leveled off at an average of 4,700 per day after a spike in November, according to the data.

White House Medical Advisor Dr. Anthony Fauci, in a news conference last month, said US health officials hope the population has enough immunity to vaccination, infection, or both to prevent the massive spike in infections and hospitalizations that the US suffered last winter omicron arrived first.

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