Omicron subvariants BQ.1 and BQ.1.1 are now dominant in the U.S. Here's what you need to know.

The coronavirus has continued to mutate, and two new Omicron subvariants have now become dominant in the U.S., according to the latest data from the Centers for Disease Control and Prevention. The subvariants, called BQ.1 and BQ.1.1, are descendants of BA.5, the Omicron subvariant that dominated infections in the U.S. since the summer. Together, they now account for more than half of infections nationwide.

BQ.1 and BQ.1.1 have also been identified in the U.K., France and other European countries, and based on modeling estimates by the European Center for Disease Prevention and Control, both subvariants could account for more than 80% of COVID-19 cases by the beginning of 2023.

When a new COVID variant emerges, there are three main questions that health experts want to answer: Is the variant more transmissible? Can it cause more severe illness? And can the vaccines and treatments available work against it?

To help answer these questions, Yahoo News spoke with Dr. Monica Gandhi, an infectious disease specialist and a professor of medicine at the University of California, San Francisco.

Are these variants more transmissible? Can they cause more severe disease?

Although not much is known yet about the two new variants, Gandhi told Yahoo News that BQ.1 and BQ.1.1 appear to be more transmissible because in some countries, including the U.S., they have taken over and replaced other variants. However, she said, it does not appear they cause more severe disease than previous strains of the virus.

“Our hospitalization, I mean I can tell you because I’m working in a hospital, our severe disease is staying low,” she said, adding that this is in part because a large percentage of the population has some sort of immunity, from either vaccination or infection.

“So many people saw the virus, so many people got Omicron-exposed during the last six months. … So we have natural immunity, we have a lot of vaccination, and that’s keeping our rates of hospitalization low,” Gandhi said.

Some infectious disease experts believe that if there is a COVID-19 surge in the U.S. driven by the BQ.1 and BQ.1.1 subvariants, it will likely be mild and short-lived based on the way the subvariants have behaved in other countries such as France. Eric Topol, a physician-scientist and director of the Scripps Research Translational Institute, wrote in a post on his Ground Truths Substack that France was the first country where the subvariants became dominant, and despite a BQ.1.1 wave in that country, “new Covid hospitalizations were on the decline throughout” that surge. He also pointed out that in New York state, which has the most cases of BQ.1.1 in the United States, there is yet to be an increase in COVID hospital admissions. This, he said, is a “positive sign.”

Are our vaccines and treatments effective against these variants?

However, the greatest implications for both of the new strains, Gandhi said, is their ability to evade immunity conferred by vaccination, treatments or prior infection. BQ.1.1 in particular has shown to be resistant to all available monoclonal antibody treatments, including Evusheld and bebtelovimab. This is worrisome because these therapies have been a vital help for immunocompromised people who don’t respond as well to COVID-19 vaccination, and also for people who cannot get vaccinated due to a history of a severe adverse reaction to the COVID shots.

Another option available to protect this population is the antiviral drug Paxlovid, which continues to be effective. But many people, including organ transplant patients, often cannot take the pill because of the way it interacts with other drugs they need. This means that in the coming months, as BQ.1 and BQ.1.1 grow in the U.S., people with weakened immune systems, such as cancer patients, could be more vulnerable to COVID-19.

But Gandhi noted that doctors are continuing to use the monoclonal antibody therapies available right now, because even though the new Omicron subvariants account for more than half of new cases, there are still other strains circulating that respond well to these treatments.

“Overall across the nation, 50% [of cases] are still BA.4 and BA.5. So we’re still using it ... but we’re probably gonna have to stop using that soon,” she said, adding that there need to be new treatments for this segment of the population in the near future. At the moment, there are no replacements for treatments like Evusheld available.

It is too soon to know exactly how effective our current COVID vaccines are holding up against BQ.1 and BQ.1.1. But Gandhi said that since these subvariants are offshoots of BA.5, the new bivalent boosters that are designed to target this and the BA.4 subvariant are also likely to work against these new Omicron strains.

In a recent press release, Pfizer said its bivalent booster protected against Omicron subvariant BQ.1.1. A month after receiving the bivalent booster, adults 55 and over were found to have a ninefold increase in antibodies against BQ.1.1, according to the company. Earlier this month, Moderna announced that its bivalent vaccine also provided protection against BQ.1.1.

However, health experts like Topol have pointed out that COVID bivalent booster uptake has been low in the U.S., particularly in people 65 and older, a group that would benefit the most from it. In a Monday tweet, he cited recent CDC data showing that nearly 90% of the deaths from COVID last month were people in this age group. He noted that their bivalent booster rate was less than 25% and said that “a high percentage of these deaths are preventable.”