Public Health

XBB.1.5 variant: What you need to know now with Andrea Garcia, JD, MPH


AMA Update covers a range of health care topics affecting the lives of physicians, residents, medical students and patients. From private practice and health system leaders to scientists and public health officials, hear from the experts in medicine on COVID-19, monkeypox, medical education, advocacy issues, burnout, vaccines and more.

In today’s AMA Update, AMA Vice President of Science, Medicine and Public Health Andrea Garcia, JD, MPH, explains what you need to know about the latest Omicron subvariant. Also covering bivalent booster efficacy, data from a new COVID study in Israel and protecting kids from the flu as they return to school after the holidays. AMA Chief Experience Officer Todd Unger hosts.

Learn more at the AMA COVID-19 resource center.


  • Andrea Garcia, JD, MPH, vice president, science, medicine & public health, American Medical Association

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Unger: Hello and welcome to the AMA Update video and podcast. Today we have our weekly look at the headlines with the AMA's Vice President of Science, Medicine and Public Health, Andrea Garcia, in Chicago. I'm Todd Unger, AMA's chief experience officer in Chicago. Welcome back, Andrea.

Garcia: Thanks. Good to be here.

Unger: Well, let's talk about XBB1.5, the subvariant that's so contagious, possibly the most transmissible strain of the virus so far. What have we learned?

Garcia: Well, last week we talked about how the CDC was reporting that XBB1.5, which is an Omicron subvariant, accounted for about 40% of COVID cases in the U.S. And because of the holidays, there were delays in reporting the data from states. So that was an estimate.

This week, we know CDC has a clearer picture with more data reported and they're now estimating that XBB1.5 accounts for about 28% of cases. That makes it the second most dominant strain here in the U.S. with BQ.1.1 still being the most dominant variant and that's responsible for about 34% of COVID cases. But that could and likely will change pretty quickly. We know XBB1.5 is already the most dominant strain in the Northeast of the U.S., and it makes up about 70% of cases there.

Unger: Are we getting a sense now of how these different subvariants are affecting our case counts?

Garcia: Well, if we look at The New York Times data, that daily average number of cases has increased from last week. There are currently about 67,000 COVID cases being reported each day. That's an increase of about 16% from seven days ago. We also know that test positivity rate is at 15% and those higher test positivity rates are also a sign that many infections are not being reported. So that case count is likely higher.

Unger: And unfortunately, from what I understand, these case counts are leading to higher rates of hospitalization and deaths. What are the specifics that you're seeing there?

Garcia: Hospitalizations and deaths have increased by double-digit percentages in the last two weeks. That daily average of hospitalizations is around 47,000. That's an increase of 18% in the last two weeks. That's the highest number of daily hospitalizations we've seen since March of 2022. And that daily average number of deaths is, unfortunately, around 500, and that's a 19% increase in the last two weeks.

Unger: Now, back to what we were talking about at the beginning, we're hearing from some experts that this particular subvariant, XBB1.5, is the most contagious variant yet. When we think about that, we've just seen kind of a chain of each variant more transmissible than the other. What is going on there?

Garcia: Well, XBB1.5 has gone from 1% to nearly 28% of COVID cases here in the U.S. pretty quickly. Scientists are reporting that it appears to bind more tightly to cells in the human body than the predecessors. It also seems to be more resistant than earlier variants to immune system antibodies. So we're likely going to continue to see that increase in cases.

We know that getting vaccinated and staying up to date on COVID boosters still remains that best form of protection from serious illness, hospitalization. And death and that updated booster offers that added protection against those variants that are currently circulating.

Unger: Still some people out there who have not had COVID yet, probably still open, of course, to getting this new subvariant. So a lot of protection that these boosters offer. Make sure to get your booster. When we think about what we're seeing in terms of symptoms from this variant, kind of the same as previous variants or worse?

Garcia: Symptoms with XBB1.5 appear to be similar to the earlier Omicron variants, and those can range from cold symptoms to shortness of breath and low oxygen levels that require emergency medical attention. I think with that being said, this new slate of variants, including XBB1.5, as it continues to spread, the signs and symptoms of COVID may seem different than what we saw earlier in the pandemic. And I think early on, we heard a lot about people losing their sense of taste and smell, at least temporarily. Well, that is still happening in some instances. It does seem to be more rare or less common with the Omicron variant.

Unger: So on one hand, we have a variant that is very, very transmissible, but on the symptoms overall are we seeing any evidence that it is less severe, more severe? Where would you put that?

Garcia: The experts generally believe that the symptoms of COVID have become less severe over time. That could be because they tend to remain in the upper respiratory tract and don't affect the lungs as much as earlier variants. But it could also be because people in the U.S. have some level of immunity from vaccines or prior infection. So many people who are infected now are reporting those mild symptoms like cough, congestion and a headache that could be confused with symptoms of the cold or flu. So if you notice any of these symptoms, you should still be testing for COVID.

Unger: Well, given all of this, I think there's still a lot of confusion about the effectiveness of the bivalent booster, which has been reflected somewhat, I guess, in its uptake. What's the news there that physicians can use to help patients understand why getting the shot continues to be so important?

Garcia: Yeah, I would echo that there's definitely still a lot of confusion out there about why these bivalent boosters are needed and there is a new study out of Israel. It's a preprint article, so it hasn't yet been peer-reviewed. But it examines the updated bivalent booster's effectiveness in preventing severe outcomes in those 65 and older. And that study found that the new bivalent boosters sharply reduced hospitalization and mortality rates in older patients. The study showed an 81% reduction in hospitalizations in people 65 and older who had received that booster compared to those who'd received two doses of a COVID vaccine but not that updated booster dose.

Unger: That seems like pretty powerful data, very convincing. Can you tell us a little bit more about the study participants, any of the details?

Garcia: Yeah, so the study occurred between September to mid-December of 2022. It looked at over 622,000 people aged 65 and older who were eligible for that bivalent booster dose. Among them, over 85,000, or about 14% had received that bivalent booster. Hospitalizations due to COVID occurred in six of the bivalent vaccine recipients and that's compared to 297 participants who did not receive that booster dose.

Death due to COVID occurred in one of the bivalent vaccine recipients compared to 73 who did not receive it. So that's pretty remarkable. The study determined that participants who received that bivalent vaccine had lower hospitalization and mortality rates due to COVID than non-recipients up to 70 days after the vaccination. The data is telling. We'll, of course, continue to keep an eye on that as that study goes through the peer review process.

Unger: Excellent. Again, those are some big and very important numbers. Andrea, let's talk a little bit about something we discussed last week, which is about what's happening in China and the COVID crisis that they're undergoing there. Anything in particular that we need to know about in terms of updates?

Garcia: Yeah, just as a reminder, China lifted its COVID restrictions, lockdowns, quarantines, the mass testing that was happening. They've also reopened international travel and dropped those mandatory quarantine periods that they were requiring of visitors to the country. I think the thing that's coming up is the Lunar New Year holiday that's going to start later this month. The WHO has warned that that holiday brings a lot of travel as people head from cities to visit families in small towns and villages, and that could spark another infection wave in China.

Estimates are about 2.1 billion passenger trips by road, rail, water and air over the Chinese New Year holiday. That's double of what we saw last year during that same period. And so we're seeing more countries around the world requiring visitors from China to take those COVID tests before departing. Since last week, we've seen Greece, Germany and Sweden join the U.S. and more than a dozen other countries to require that negative COVID test from travelers coming from China. I think there is some concern that this is really not going to curb the spread of the virus, but many global health officials have raised concerns about the lack of clear epidemiologic information coming out of China.

Unger: All right, well, we'll keep our eye on that as well. Let's turn the attention here now to a different virus, influenza. So last week, we talked about cases declining, but of course, that was reporting before the holidays. Any change since kids have returned to school?

Garcia: Well, according to the CDC, we are still seeing influenza activity that remains high, but it continues to decline in most areas of the country. We haven't seen an increase from holiday gatherings. We'll keep an eye on that. It's too soon to tell, I think, what effect returning to school will have on spread. I know many kids are just getting back to school this week. That proportion of laboratory specimens, the positive tests have declined nationally for the third week in a row, but it's still possible that the current wave of flu activity could continue for weeks.

Flu is unpredictable. We often hear if you've seen one flu season, you've seen one flu season. So it's possible that the country could experience a second wave of flu and that's been true in the past. CDC is still recommending getting a flu vaccine as long as flu virus is circulating. So it's not too late to get that flu shot if you haven't already. And as a reminder, everyone six months and older, with rare exceptions, should get that flu vaccine every season.

Unger: Absolutely. And let's hope that downward trend on flu continues and we'll keep you updated as news comes in on that. That's it for today's episode. Andrea, thanks again for being here. We'll see you next week for another update. You can find all our videos and podcasts at Thanks for joining us today and please take care.

Disclaimer: The viewpoints expressed in this video are those of the participants and/or do not necessarily reflect the views and policies of the AMA.