How A Mutation Made This Year’s Flu Season So Bad

FLORA LICHTMAN: Hey, it’s Flora Lichtman, and you’re listening to Science Friday.

SPEAKER 1: The superflu is here, and it’s wreaking havoc across the nation.

SPEAKER 2: Health officials confirm a new strain of the flu is spreading. It’s very contagious, and it lasts longer.

SPEAKER 3: Here in the United States, the number of children hospitalized for the flu hitting the highest weekly rate in more than 15 years. That’s not good.

FLORA LICHTMAN: No, it is not good. The so-called superflu has sickened more than 19 million people in the US so far this season, and the flu shot hasn’t offered that much protection. So what is going on with this superflu storm? Here to cough up some answers is Dr. Jennifer Duchon, pediatric infectious disease specialist at Mount Sinai Hospital in New York. Welcome, Jen.

JENNIFER DUCHON: Hi. Thank you for having me.

FLORA LICHTMAN: Let’s talk branding. Is it a superflu? Does that actually mean anything?

JENNIFER DUCHON: So that is a little bit sensational. Certainly, we’ve seen a lot of cases of flu, and people are sick with it. But in terms of that terminology, we can break it down into case numbers and virulence. So is it a superflu in terms of virulence? So is it causing people to have more severe disease? The jury’s still kind of out on that. In terms of case numbers, absolutely. We’re seeing a lot more cases of the flu this year.

FLORA LICHTMAN: I know people who got vaccinated for flu still got really sick. Did the vaccine miss the mark? What happened there?

JENNIFER DUCHON: Yeah, so that’s really interesting. And that’s really one of the reasons why I love my profession, because there are always surprises. So the flu vaccine is made in advance of the flu season, using a combination of microbiologic and global surveillance data, as well as some modeling. Last year’s strains are modeled to see how they’re going to change. And the yearly flu vaccine is targeted to that strategy. So–

FLORA LICHTMAN: And last year in the US or Southern hemisphere strains that might come our way?

JENNIFER DUCHON: Global, global. We have global surveillance data. The WHO, in conjunction with many different nations, actually has biologic data from strains that are collected through various laboratories. And so we’re able to do some pretty sophisticated modeling in terms of how global flu strains are going to mutate or change for the next season.

So what generally happens– so they make the flu vaccine, and what we usually have first is the Southern hemispheric data. That’s because their summer’s our winter. Our winter is their summer. So as flu is generally a winter/spring virus, the Southern hemisphere sees it first.

So everyone, as typical, got the flu vaccine as they normally would in the Southern hemisphere. And what seemed to happen is that one of the flu A strains in H3N2 developed some mutations on one of the antigens. What we noticed was this H3N2 strain called subclade K had a couple of different mutations. And so the vaccine that we had developed didn’t really cover this very well.

FLORA LICHTMAN: And then it’s sort of too late, right? Because the vaccine has already been developed.

JENNIFER DUCHON: Right, exactly. So I can tell you that because these are mutations and not dramatic shifts, the flu vaccine does still protect against major complications of the flu. That includes severe pneumonia, hospitalizations. So we’re still recommending that people get the flu vaccine. But, yeah, I mean, flu is tricky. And it’s kind of interesting. There are some reports now that are showing that the Southern hemisphere is actually having a second peak of flu with this particular what we call subclade.

FLORA LICHTMAN: This super K, as it’s been dubbed in the media.

JENNIFER DUCHON: Yeah, yeah.

FLORA LICHTMAN: I mean, is the K subclade, is this like a new twig on the flu family tree?

JENNIFER DUCHON: Yeah, that’s kind of actually a good way to describe it. So it’s within the strain of H3N2. But what happened is a couple of the proteins basically mutated. So they mutated by surprise, which, again, is a feature of the flu. We know it mutates every year. And often we’re surprised.

For example, we saw an entirely new strain in 2009, the H1N1. This is a little bit different than that. So this isn’t an entirely new strain. This is basically just what we call antigenic drift. Some of those antigens have mutated and drifted.

FLORA LICHTMAN: You mentioned that the flu shot can still be protective against the most severe disease. Can we get nerdy for a second? How does that work? If it’s not a match for K, this K subclade, how is it offering protection?

JENNIFER DUCHON: Yeah, so those proteins aren’t completely changed. So they don’t mutate such that the flu vaccine doesn’t recognize those and stimulate your immune system to recognize those proteins completely. It’s more of a partial protection. And every year, the CDC studies what happened, usually at the end of the flu season, and reports that. And the H3N2 strain is usually the one that’s the trickiest. And this, again, is the one that had those antigenic drifts.

FLORA LICHTMAN: Wait, why is this– why is H3N2 the problem child?

JENNIFER DUCHON: You know, probably because, again, it seems to have the most ability to mutate and change. That’s not a hard and fast rule. But that’s the one that we seem to grapple with the most. So there are multiple flu strains that are put in the flu vaccine. Since the H1N1 came about, we’ve been including that. There’s the H3 strain, and there are also some flu B strains.

And that’s another reason why it’s really important to get vaccinated, because right now about 90% of circulating flu strains are this H3N2 subclade K. But that may change throughout the season. Last year, we saw sort of a late peak of influenza B. And that’s pretty well covered by the flu vaccine.

FLORA LICHTMAN: Yeah. I mean, is there any hope for solving this mismatch problem, like a universal flu vaccine or a different way of doing things?

JENNIFER DUCHON: There’s always hope. Although usually I have to say, I’m sort of Debbie Downer. I’m the person that you don’t want to have at your dinner party.

FLORA LICHTMAN: I love Debbie Downers. You’re always invited to my dinner party. We can Debbie Down together.

JENNIFER DUCHON: We can sit in a corner and talk about flu. So, yes, unfortunately, some of that research has been put on the back burner. There–

FLORA LICHTMAN: You don’t say.

JENNIFER DUCHON: Interesting, right? So there is a global effort to develop what’s called a universal flu vaccine. Some of those efforts involve mRNA technology. Some of them don’t. But that’s been put on the back burner for the time being, especially in the US, where a lot of our vaccine research has unfortunately been affected by recent changes in the CDC architecture.

FLORA LICHTMAN: Well, speaking of that, I mean, earlier this year, the CDC changed recommendations for childhood vaccines and stopped universally recommending that kids get the flu vaccine. What are your thoughts on that a pediatric infectious disease specialist?

JENNIFER DUCHON: Yeah. So that’s an unmitigated disaster, huh? So we know that, even by the CDC’s own data, that children have the highest hospitalization rate next to the elderly. So making those recommendations is really grossly irresponsible. And I’m not the only one that feels that way. I think that infectious disease physicians, general pediatricians, anyone who works with children is just really disappointed by those recommendations.

FLORA LICHTMAN: Are fewer people getting the flu shot this year? And is that a factor in why we’ve seen so many cases?

JENNIFER DUCHON: It’s definitely a contributing factor. And yes. The flu vaccine is one of those vaccines that tends to have poor uptake anyway. So about 43% of eligible children this season thus far have been immunized. Of course, that’s terrible.

There are a lot of reasons for that. It’s annually– if people are going to skip something, they’re going to skip something that you have to remember to get every year. I really give a lot of credit to the general pediatricians that I work with. They’re on the ground and trying to do their best in making sure that everyone comes in for their visit. But it can be challenging. So also the elephant in the room, or not such an elephant in the room, is that certainly since COVID, vaccine uptake, especially for flu, has been diminished.

FLORA LICHTMAN: Yeah, yeah.

JENNIFER DUCHON: And I sort of am– I mean, a lot of this renders me speechless, unfortunately. I’m sorry that we got here. And I’m really hoping that it doesn’t take a long time to reverse course, but I don’t know that that’s necessarily the case.

FLORA LICHTMAN: Wow. It renders you speechless?

JENNIFER DUCHON: Yes, it really does.

FLORA LICHTMAN: Say more about that.

JENNIFER DUCHON: Well, I’m speechless.

FLORA LICHTMAN: Touche.

JENNIFER DUCHON: Touche.

FLORA LICHTMAN: OK, I want to wrap up with a different kind of question.

JENNIFER DUCHON: Yeah.

FLORA LICHTMAN: You’re a doctor. When you go down with the flu, what’s your remedy? Rewatching Mad Men? Ginger shots? What do you do?

JENNIFER DUCHON: So I personally prefer to kick everybody out of the room, close the door, not speak to anybody. That doesn’t work. Usually what I end up doing is working from home. But we do, by the way, have antivirals that can help shorten the duration of flu if you get it and you start to take those medications in a timely manner, can help prevent the really severe consequences of flu, such as pneumonia, hospitalization, dehydration.

So I already have my prescription in lock for one of those particular medications. We kind of forget that one of the reasons to test is to be able to use one of those treatments, one of those therapies.

FLORA LICHTMAN: OK, so take some medicine and kick everybody else out of the room.

JENNIFER DUCHON: Yeah, yeah. And one of the TV stations where I live has 24/7 Law and Order marathon. So that’s what I like to do. My husband prefers Storage Wars, but we have two TVs, so it’s fine.

FLORA LICHTMAN: Dr. Jennifer Duchon is a pediatric infectious disease specialist at Mount Sinai Hospital in New York. Jen, thanks for joining us.

JENNIFER DUCHON: Thank you.

FLORA LICHTMAN: This episode was produced by Kathleen Davis. And if you have a question or a comment or something you want us to look into, please give us a ring. 877-4-SCIFRI. 877-4-SCIFRI. The listener line is always open. See you tomorrow. I’m Flora Lichtman.

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