Omicron BQ, XBB subvariants trigger greater than 70% of infections

People wait to take tests for coronavirus disease (COVID-19) at a pop-up testing site in New York City on July 11, 2022.

Brendan McDermid | Reuters

The most immune-avoidable omicron subvariants to date now cause more than 70% of new infections in the US as millions of Americans prepare to travel and gather with family for the holidays.

Subvariants BQ.1 and BQ.1.1 combined now account for 68% of new cases, according to data released Friday by the Centers for Disease Control and Prevention. The XBB subvariant causes 4.7% of new Covid infections.

Scientists have described the BQ and XBB subvariants as better at evading immunity from vaccination and infection than previous versions of the virus in several independent studies.

They pose a significant threat to people with compromised immune systems because key antibody treatments are resistant to them. The Food and Drug Administration last week pulled bebtelovimab, a monoclonal antibody used to prevent people who contract Covid from developing serious illness.

Bebtelovimab has been used by people who cannot take other FDA-approved treatments, such as the antiviral Paxlovid. Many people with weakened immune systems, such as B. Organ transplant patients cannot take Paxlovid with their other medicines.

The BQ and XBB subvariants are also resistant to Evusheld, an antibody cocktail that many people with compromised immune systems rely on for protection because they do not respond adequately to the vaccines. The FDA continues to approve Evusheld for use.

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According to a recent study, the Omicron boosters also elicit a weaker immune response against the BQ and XBB subvariants than against the previously dominant version of the virus. The shots were developed against the BA.5 subvariant, which now causes only 11% of infections in the US

Although the boosters are probably less effective against the BQ and XBB subvariants than against BA.5, they still elicit an immune response. Pfizer found that the new boosters perform better against the BQ.1.1 and XBB than the original shots.

White House Medical Advisor Dr. Anthony Fauci, in a press conference last month, said the boosters will still provide protection against the weaker sub-variants, albeit not at optimal levels. Fauci said the protection drops a bit with BQ.1.1, but drops many times over against XBB.

According to experts, the shots should offer better protection against hospitalization than infections and minor illnesses.

Covid infections and hospitalizations rise after the Thanksgiving holiday. According to CDC data, cases rose nearly 50% to about 459,000 in the week ended Dec. 7, compared to 307,000 the week before. This is an undercount because the official data doesn’t include results from people testing at home.

Week-over-week hospital admissions for people with Covid have increased by about 14% to an average of more than 4,800 admissions per day, according to CDC data. More than 50% of hospital patients are over 70 years old.

CDC Director Dr. Rochelle Walensky encouraged the public to mask up this winter to prevent the spread of respiratory illness, particularly people living in counties with high Covid levels.

The CDC is calling on everyone who is eligible to receive their Covid booster and flu shots to help reduce the burden of disease this winter.

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