URMC infectious disease doctor explains why this flu season has been nastier than usual and why the vaccine only helps to a certain extent as it’s developed based on relatively old data
By Chris Motola
Q: So, what’s up with this flu season? It seems like it’s been nastier than usual.
A: Well, it’s the second year in a row we’ve had a fairly robust flu season. I don’t know that it’s hugely different than pre-pandemic times. We had some fairly anemic flu seasons during the pandemic, mostly because of people’s behaviors and patterns. Most of us were avoiding a lot of big social gatherings, masking, washing our hands, just being a little more vigilant during the pandemic. And in the immediate years following the pandemic, I think we’ve slowly returned to natural behaviors to some extent and that’s allowed for larger flu outbreaks this season than we’ve had recently. The other thing that’s different, of course, is that because we weren’t getting infected as a community locally, nationally and internationally for that matter. That led to less natural immunity. Natural immunity, when combined with vaccines, is the best protection you have. So, if you had the flu two years ago and this year you got vaccinated as well, then you are probably less likely to get the flu than if you hadn’t had an infection a few years ago. So that hybrid immunity has always been sort of our best defense against large outbreaks. And I think during the pandemic, because we weren’t having outbreaks of influenza and people weren’t getting sick, that sort of allowed for less natural immunity. So that could be why we’re seeing more robust outbreaks this year and last.
Q: So, with endemic viruses like the flu, is it accurate to say our immune system modulate over time along with the mutations of these diseases, assuming we, as a species, are getting infected?
A: Yeah, so when you get infected with a virus like flu, COVID or other RNA virus, while the virus is in you and replicating, making more copies of itself, it also is undergoing these micro mutations. And so your immune system and how it adapts responds to you being naturally infected. It does a pretty good job of giving you sort of a broadly protective immune response. That happens to some extent with vaccines too. But again, the best kind of immunity is hybrid immunity where you have this adaptive defense that’s a combination of having been exposed in different ways either to a part of the virus with vaccination or the whole virus with natural infections, with micro mutations and all these different things.
Q: Moving on to the vaccines, how effective were they this year? And how often do we hit the mark with them? And are there still benefits even when we miss?
A: Well, I think it’s important to keep in mind that this season’s vaccines were made based on viruses that were circulating in the southern hemisphere two summers ago, not this past summer, but summer 2024. That’s because of the technology that’s needed to make these vaccines and how long manufacturing and production take. And then how long it takes to identify the strain, understand the strain, get that strain approved by bodies like the FDA and then to actually manufacture or produce the vaccines. So, it takes minimum of 10 months, which is why we can’t usually make a vaccine for this season based on what we saw in the southern hemisphere this past summer for example. And that would be ideal. Because whatever was circulating in Australia in the summertime for us, which would have been June, July, August is probably what’s going to be infecting us in November, October, December and January. So, if we could have technology that will allow us to develop vaccines that quickly that would be ideal. The only technology available that allows that for that right now is mRNA technologies and flu vaccines aren’t generally made using mRNA technology. So that’s part of always been one of the problems with influenza vaccines. You are basing it on older data and the viruses in the meantime have over a year to undergo further mutations. So, there is always a possibility and a high likelihood that there is going to be some degree of mismatch with the strain that’s circulating now. But those mutations are usually small enough that you do still have fairly effective vaccines. They won’t necessarily prevent illness, but they’ll prevent severe disease, which is really the goal of these vaccines most of the time. They’ll prevent hospitalizations; they’ll prevent deaths.
Q: How about this year?
A: Occasionally, we have a season where the virus has mutated so much that there is a fairly large mismatch and that’s something that we’ve been seeing this year where one of the strains that’s in the flu vaccine, the H3N2 strain, is very different than the H3N2 strain that’s actually circulating and causing illnesses this year.
Q: Are you seeing any trends with the flu vaccine uptake, particularly since the pandemic?
A: I think it’s a little lower than it was, say, five or six years ago. I think that in higher risk populations like older adults and those with underlying chronic conditions, it seems to be similar. But rates are lower for children. Rates are lower for healthy, younger adults and younger adults in general. So, yeah, there’s less uptake this year than there had been pre-pandemic.
Q: Do you think some of that is fallout from how politicized the COVID vaccines became during the pandemic?
A: I think that vaccine hesitancy and skepticism is not a new thing. I think we have faced these problems for decades. I think that the awareness of the link between the federal government and healthcare policies in general was certainly more publicized during the pandemic and I think that people now associate vaccines with federal policies. Whereas maybe pre-pandemic they associated vaccines with healthcare policies, with what their doctors were saying, with what hospitals were saying. I do think that link does have an impact and can polarize how people sometimes feel about vaccines. But I don’t think that vaccine hesitancy or skepticism, particularly around the flu vaccine, is a new thing. Even before the pandemic, my patients would tell me, “I am not going to get flu vaccine because the last time when I got it, it gave me the flu.” And I said no that’s absolutely not true, it cannot happen. But you know these are things that we as physicians have heard commonly for our entire practice. So, I think it’s now behooves the practicing clinician to maybe work a little harder to help their patients understand why we recommend vaccines.
Q: The flu’s been with us for a long time. So, it’s not exactly novel, but what’s something the average person might not know about it?
A: Most people don’t recognize that in any given season at least three flu strains circulate and cause infections. So even if you are hearing in the news that the vaccines don’t work against one strain, that doesn’t mean it’s not protecting you against the other two. So we still recommend people go out and get vaccinated because if you were lucky enough not to get an H3N2 infection and even if you did, you’re still susceptible to getting infected with a different strain in February, March or April if we have another outbreak, which we almost always do. So, the vaccine is doing more than you think it is and there’s more risk to the flu than you think there is. It’s not just one virus. It’s almost like three viruses, sometimes four, that collectively we call influenza.
Q: What got you interested in infectious diseases?
A: Well, infections are the No. 1 threat to humans, to humanity, from a medical standpoint. It is an equal opportunity threat because it does not respect age, it doesn’t respect gender, culture, class, geographical boundaries. We’re all at risk. We’re all going to get infected. And it can affect pretty nearly every single system in your body. You can have brain infections, lung infections, bone infections. So, I like the impartiality of it and the investigative nature of it and how you have to really take into consideration the patient sitting in front of you and what their exposure risks are. Things that they do in their lives that might predispose them to getting certain kinds of infections and then almost for almost every infection and every patient, treatment is often very individualized and very tailored to the person. So, it does allow you to have sort of a precision medicine approach to thinking about disease and healthcare.
Lifelines
Name: Angela Branche, M.D.
Position: Associate professor of medicine at University of Rochester School of Medicine, specializing in infectious diseases
Hometown: Kendall Park, New Jersey
Education: Bachelor of Arts degree in biology from the University of Pennsylvania and Doctor of Medicine (MD) at American University of the Caribbean. Completed residency in internal medicine at NYU Langone
Affiliations: URMC Health system
Organizations: Infectious Disease Society of America, National Institutes of Health (NIH) Infectious Diseases Clinical Research Consortium
Hobbies: Church activities, music, reading, biking