“I’m not talking about a sniffle”: Doctor Isaac Bogoch on the myths and realities of a harsh flu season

Earlier this week, Ottawa public health reported the deaths of three children linked to complications with influenza. These tragic losses are the most extreme examples of a flu season that is wreaking havoc across the country. “People think the flu is like sniffles or a bit of a cough—that is not what we’re talking about,” says Isaac Bogoch, an infectious disease specialist at Toronto General Hospital. Many Torontonians know Bogoch as the doctor who got us through Covid one daily update at a time on CP24. Here, he answers our burning questions about this year’s flu season, including what’s up with H3N2 and why it’s definitely not too late to get your flu shot.

Hi, Dr. Bogoch. How are you doing? I’m terrible. Thank you for asking. I’m sitting in my office on the 14th floor of Toronto General Hospital. The wards and the emergency rooms are both just a few seconds away.

I just read that ICU admissions for the flu are up 127 per cent in Ontario. Is that what you’re seeing? I would be careful with any stat. The deal is that it’s winter in Canada, so no one is surprised that we’re seeing influenza. We’re going to see it every year around this time, forever. So what’s new about this year? One thing is that the flu season started in late October, a bit earlier than it normally starts. It’s probably—the keyword being probably—going to end a bit earlier than it normally does, which could balance things out. The second thing is that we talk about “the flu” like it’s one virus when in fact there are three circulating flu viruses: H3N2, H1N1 and influenza B. What changes is which strain is dominant. This year, that’s H3N2, and if you look back in history, that tends to mean a more significant flu season.

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Because it’s stronger than other strains? It relates to the virulence of the virus—not all influenza strains are created equal. Any flu can cause significant illness on an individual level. At a population level, H3N2 tends to be more severe. And then the third factor is this year’s vaccine. Every year, researchers compile data to make their best educated guess at which strain will be dominant and create the vaccine to address that prediction. Some years we get a very close match between the vaccine and the circulating virus. This year, the component that protects us against H3N2 is not as protective as we would like it to be.

Why is that? It takes a long time to make these influenza vaccines. You produce them in eggs, and then you have to mass-produce them. So the experts are looking at the circulating strains months and months in advance. What’s happened is that the H3N2 virus that is circulating today has mutated such that the match between the vaccine and the circulating virus is not as ideal as we’d like it to be. I’m choosing my words carefully, because people will say, Oh, it’s a mismatch—I’m not going to get it. But that’s the wrong answer. The flu shot is still protective for two reasons: it still offers some protection against H3N2, and it protects rather well against the other two flu stains, which are still circulating.

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Is it enough to at least prevent a worst-case scenario? You can’t talk specifics for 41 million people, but in general, the influenza virus vaccine will reduce your risk of getting the flu. Of course, it’s not perfect, and some people are going to get the flu shot and still get sick, but it still reduces your risk of getting the flu. And if you do get the flu, it can reduce and mitigate the severity of symptoms.

Could it be the difference between a day on the couch watching Netflix and a visit to an overcrowded hospital? In general, yes. Anyone can get severe flu, but it is more common in the elderly, in infants and young children, in pregnant women, and in people with underlying medical conditions. So those are the groups most likely to end up in an ICU, and a flu shot will reduce the risks for severe outcomes for those people as well.

What about people who are not in those higher-risk groups? They should still get the flu shot. People talk about the flu like it’s the sniffles, a little cough. It’s not. It’s a nasty virus that can totally wallop people. And while an otherwise healthy 25-year-old is very unlikely to end up in hospital, they can still get absolutely demolished and be down for two or three days. Have you ever been felled by the influenza virus? Like really knocked down?

I don’t think I have. Well, if you had been, and then someone came along and said they could make it 50 per cent, 30 per cent, even 10 per cent better, I think most people would welcome that opportunity.

The most recent federal data shows that over 20 per cent of flu tests are now coming back positive, with the most detections among people ages 19 and under. What does that tell you? It’s important to recognize that detection rates may be the result of health-seeking behaviour. So parents are more likely to bring a sick kid in for a test. What’s more important is outcomes: of the people who do test positive, who is sick enough to end up in the hospital? If you look at the Public Health Agency of Canada’s rate of hospitalizations data, you see the oldest and the youngest (under the age of five), which is what we see year after year after year. It’s unfortunate, but it’s not unexpected.

Earlier this week, Ottawa reported three flu deaths in children in the past month. Does that reflect anything notable? The flu is a terrible disease in the youngest and the oldest. I don’t want to normalize it, but we know who the flu is most likely to be severe in. It’s awful. It’s absolutely tragic, and thankfully it’s not something we see a lot of, but it’s not surprising.

I read that, since H3N2 doesn’t come along all that often, young people may be encountering it for the first time. Is that true? And if so, could it result in more extreme cases in children? Maybe, but I would not be overly confident on that. We have to be humble with these speculations.

How challenging does this year feel compared with last year’s flu season? We’ve been through Covid, okay? It’s a flu season. People are getting the flu, and they’re coming into hospital. We’ll care for them when they’re here. The key thing is prevention: get your flu shot; stay at home if you’re sick; keep your kids home from school if they’re sick, so they don’t infect others; improve the quality of air and indoor environments, because that helps reduce the risk of transmission of viruses in indoor settings where the vast majority of these are transmitted; wash your hands. We’re well beyond the era of mask mandates, but you can put on a mask to reduce your risk of infection. It’s absolutely simple steps.

I’m feeling a bit of pandemic déjà vu. You shouldn’t be. If you’re billing this as Covid redux—that’s false. Hallway medicine has been around for more than a decade. Every single December, you will see the same headlines: flu season, hospital pressure, hallway medicine, busy emergency departments. Of course, some years are better or worse. If I had to bet, I would say that, when we look back on 2025, we will see that this was a more-severe-than-normal flu season. You can tell ahead of time—we look at the southern hemisphere as an imperfect barometer for what our flu season is going to look like. Australia had a very bad flu season, and it seems like we are now in the midst of a very bad flu season. But we can handle it.

What role could vaccine hesitancy be playing in a harsh flu season? Flu vaccination rates tend to be pretty consistent around 40 per cent. I think people who never got the shot are continuing to not get it, and people who did get it are continuing to get it.

Last year, 43 per cent of Canadians got the flu shot. This year, it’s only 33 per cent. Isn’t that a notable dip? It’s only mid-December, though. That percentage could rise when they make the final tally.

Is there a particular vaccine myth you’d like to bust?
The flu shot gave me the flu. That doesn’t happen. And then the other key point is that it is not too late to get vaccinated. The vaccine will still help reduce your risk of getting the flu, and if you do get the flu, it will reduce the severity.

This interview has been edited for length and clarity.