The omicron variant family tree has grown significantly over the past year. Brood now includes a sub-variant soup with alphanumeric names such as BA.2, BA.5, and BF.7. The US Centers for Disease Control and Prevention estimates that two versions – BQ.1 and BQ.1.1 – caused just over half of new infections in the United States during the week ending January 7.
Now, a newcomer dubbed XBB.1.5 looks set for a ramp-up. According to CDC estimates, it accounts for more than 80% of new cases in parts of the northeastern United States. For the week ending January 14, it was responsible for 43% of new cases across the country.
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But while previous variants such as the original alpha, delta, and omicron were linked to massive waves of new infections, it’s not yet clear whether XBB.1.5 is destined for a similar path (SN: 12/21/21). Preliminary evidence suggests that the sub-variant, dubbed the Kraken in some circles, is more transmissible than its predecessors. This trait, however, is a hallmark of viral evolution – successful new variants must be able to out-compete their siblings (SN: 05/26/20).
For now, experts from the World Health Organization are keeping a close eye on XBB.1.5. But it’s too early to tell if he could conquer the world. Most cases are currently coming from the US, UK and Denmark.
Scientific News spoke to infectious disease expert Peter Chin-Hong of the University of California, San Francisco about the latest coronavirus variant to make headlines. The conversation has been edited for length and clarity.
NS: What is the difference between XBB.1.5 and earlier versions of omicron?
Chin Hong: There are many variations that are being produced all the time. This is a normal thing for the virus because the virus makes more copies of itself. It’s not exactly accurate or exact, so it makes mistakes, [which are the variants]. It’s a bit like a bad photocopier in the office.
XBB, a sibling of XBB.1.5, was scary – and it showed in the fall of 2022 – because it was one of the most evasive variants of the immune system. But the reason XBB never took off in the world – it was really in Singapore and India – was that it didn’t really infect cells as well.
XBB.1.5 has the immune slipperiness of XBB, but it also has this new mutation that makes it easier for cells to infect. It’s a bit like a bulldog that won’t let go of the cell. While XBB was somewhat invisible, as if he had the invisibility cloak of Harry Potter, he didn’t have the bite. But XBB.1.5 has the invisibility cloak, plus the bite.
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NS: Is that why it spreads so effectively in certain areas?
Chin Hong: We think so. Because being very good at infecting cells is a very important superpower if you’re a virus.
You can be invisible [to the immune system] whatever you want, but if you don’t infect the cells effectively, you probably won’t be as infectious. It could be [the reason] XBB.1.5 is spreading because it has these two advantages. Seeing how this crowds out the other variants now makes us worry that this is something to pay attention to. And this is accompanied by an increase in cases and hospitalizations.
NS: Previous variants were linked to strong outbreaks of infections. Can we expect the same from XBB.1.5?
Chin Hong: It is complicated. If it was March 2020, it would be a very simple answer: Yes. But in January 2023, you have so much variation in the amount of experience people have with COVID, even if it’s a different type.
You may have someone who has been infected two or three times in addition to being vaccinated and vaccinated. It will be someone who is really, really well protected against serious illness. Maybe they could catch a cold. Maybe they wouldn’t even know they have an infection compared to someone who hasn’t been vaccinated and has never been exposed and is older. It might as well be March 2020 for them.
That [second] kind of person is, for example, in China. In China, XBB.1.5 could cause a lot of problems. But XBB.1.5 going, you know, to midtown Manhattan might not cause as much of a problem in a highly vaccinated and exposed group of people.
[Timing also matters] because we’ve seen a lot of BQ.1, BQ.1.1 recently, and a lot of people got infected after Thanksgiving. This rise of XBB.1.5 comes after many people have already been infected recently. So it probably won’t do as much damage as if you had a long lull and all of a sudden you have this new thing.
NS: Do vaccines and treatments still work against it?
Chin Hong: Newer updated boosters generally work a bit better than older vaccines in terms of overall effectiveness and infection prevention. But with these new slippery variants like XBB.1.5… if you’re looking to prevent infection, even a mild infection, vaccines will probably last maybe three months.
But if you’re talking about preventing me from dying or going to the hospital, these vaccines are going to give me extra protection for many, many months, probably until next winter for most people. For older people, over 65, if they’re not boosted today, that’s a problem.
[Drugs such as] Paxlovid and remdesivir work independently of spike protein [the part of the virus targeted by vaccines but where many of the defense-evading mutations are (SN: 3/1/22)]. So it doesn’t matter which variant’s invisibility cloak. They’re going to work because they’re working to shut down the virus factory, which is one of the first steps, before the spike protein is made.
So they will work no matter what [spike] variant is coming, which is a good thing. Even if you have not been vaccinated or never been exposed, if you are diagnosed and receive treatment early, it will significantly reduce your hospitalization rates.
Now not all monoclonal antibodies work. [The virus has changed too much (SN: 10/17/22).]
NS: Why do only omicron variants appear?
Chin Hong: I think omicron has found a magic formula. It’s going to be tough to kick him out of the gold medal stand. It’s so good for transmission, and all those other things that are good for the virus.
In the [earlier] days, it was two or three months, and you had a new variant of coronavirus somewhere in the world. Now it’s been omicron for two Thanksgivings.
NS: With each variant being more transmissible than the last, is it inevitable that everyone will get COVID?
Chin Hong: People who haven’t been infected before are going to have a really hard time escaping this one. But it is not impossible. It’s going to be harder and harder, not only because XBB.1.5 is so transferable, but also because we don’t have as many restrictions anymore. You go to the grocery store, nobody wears a mask or you don’t feel like you have peer pressure to wear masks. So you are going to be exposed just as you are exposed to the common cold….
But you can reduce the short-term risk by getting a booster, if you don’t already have one. And certainly [the booster] may reduce the risk of dying, especially if you are older or immunocompromised….
[People still wearing masks] must wear very good quality masks [such as KN95s] because you can’t rely on everyone wearing masks anymore.
NS: How worried should people be about XBB.1.5?
Chin Hong: The world is divided into two groups of people. People whose bodies are very, very experienced with COVID – it’s had vaccines or a boost or… a few infections. And then there are people whose bodies are not well accustomed to COVID. For that [latter] group, they should be worried.
For someone, you look around and your neighbor figured it out and nothing happened, or your cousin or someone at work, and it’s like it’s no big deal. But there are still 500 people dying every day in the United States [from COVID]. And for these people, it’s huge….
It’s a weird situation because it’s not a one-size-fits-all solution anymore and different people have different levels of risk.