New XBB COVID variant spreading quickly

By Dr. Eve Glazier and Dr. Elizabeth Ko
Posted2/5/2023 7:00 AM

Q: I live in Boston, and the news here seems to be fixated on a new COVID-19 variant. Omicron was all everyone talked about for a long time. Does this mean the new variant we are hearing about is worse? What are we supposed to do to protect ourselves?

A: You're referring to XBB.1.5, an offshoot of the omicron variant. Omicron is itself one of the numerous descendants of SARS-CoV-2, the novel coronavirus that launched the COVID-19 pandemic three years ago. The reason you're hearing so much about this new variant, which is being referred to simply as XBB, is that it has become the dominant strain of the novel coronavirus in your area.


According to the Centers for Disease Control and Prevention, genetic testing suggests that the majority of new cases of COVID-19 in the northeastern U.S. are now caused by XBB. Nationally, XBB has gone from causing fewer than 2% of COVID-19 cases at the end of 2022 to more than one-fourth of all cases at the start of 2023.

While XBB has proved to be more contagious than its predecessors, it does not appear to be more dangerous. At this time, there has not been a spike in either hospitalizations or deaths due to XBB infections. However, this will likely change as the variant continues its geographic spread.

As with all viral variants that begin to circulate in great numbers, the success of XBB is due to the presence of certain mutations. In coronavirus variants, mutations include changes to the spike proteins on the outer shell. These structural changes make the variants more successful at slipping past the body's existing defenses. This includes evading both naturally acquired immunity and immunity conferred by vaccines and boosters.

What's particularly worrisome is that XBB has arrived at a time when vaccination rates against COVID-19 have dropped precipitously. Only 15% of those who are eligible have received the newer bivalent vaccine, which was developed with the variants in mind. On top of that, the majority of people in the U.S. have largely stopped taking protective measures, including the use of masks. That, along with indoor living that is necessitated by the cold winter weather, has increased the risk of infection.

And that brings us to your final question, which is how to guard against infection with XBB. The answer is to get back to the basics. It's crucial to stay up to date with coronavirus vaccines and boosters, which have proved to be effective in protecting against severe illness. We urge anyone who hasn't yet received the bivalent booster to do so. When spending time in public places, wear a good-quality and well-fitted mask. If you do become sick with COVID-19, see your doctor. Antiviral medications can ease symptoms and shorten the duration of illness. The coronavirus and its variants are with us for the foreseeable future. It's up to us to remain vigilant and protect ourselves and those around us.

• Dr. Eve Glazier is an internist and associate professor of medicine at UCLA Health. Dr. Elizabeth Ko is an internist and assistant professor of medicine at UCLA Health. Send your questions to

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