People wait to take coronavirus disease (COVID-19) tests at a pop-up testing site in New York, July 11, 2022.
Brendan McDermid | Reuters
The most immune omicron subvariants to date are responsible for more than 70% of new infections in the United States, as millions of Americans prepare to travel and reunite with families for the holidays later this month.
The BQ.1 and BQ.1.1 subvariants taken together are now responsible for 68% of new cases, according to data released Friday by the Centers for Disease Control and Prevention. The XBB subvariant is responsible for 4.7% of new infections.
Scientists in several independent studies have described the BQ and XBB subvariants as being better at evading immunity against vaccination and infection than previous versions of the virus.
They pose a significant threat to people with weakened immune systems because major antibody treatments are resistant to them. The Food and Drug Administration last week withdrew bebtelovimab, a monoclonal antibody used to prevent people who catch Covid from developing serious illness.
Bebtelovimab was used by people who couldn’t take other FDA-cleared treatments, such as the antiviral drug Paxlovid. Many people with weakened immune systems, such as 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 weakened immune systems rely on for protection because they do not mount an adequate response to vaccines. The FDA still authorizes the use of Evusheld.
The omicron boosters also elicit a weaker immune response against the BQ and XBB subvariants than against the previously dominant version of the virus, according to a recent study. The injections were designed against the BA.5 subvariant, which now causes only 11% of infections in the United States.
Although 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 do a better job against BQ.1.1 and XBB than the original shots.
White House chief medical adviser Dr. Anthony Fauci at a press conference last month said boosters would still provide protection against the more evasive immune subvariants, but not at an optimal level. . Fauci said protection drops a bit with BQ.1.1, but drops several times against XBB.
Injections should offer better protection against hospitalization than mild infections and illnesses, experts say.
Covid infections and hospitalizations rise after Thanksgiving holiday. Cases rose nearly 50% to about 459,000 for the week ending Dec. 7, from 307,000 the previous week, CDC data shows. This is an undercount because official data does not include results from people testing from home.
Hospitalizations of people with Covid have increased by about 14% week over week to more than 4,800 admissions per day on average, according to CDC data. More than 50% of people hospitalized are aged 70 and over.
CDC Director Dr. Rochelle Walensky encouraged the public to wear masks this winter to help prevent the spread of respiratory illnesses, especially people who live in counties with high levels of Covid.
The CDC is calling on everyone who is eligible to get their Covid booster and flu shot to help reduce the burden of illness this winter.