Annual flu shots can reduce stroke risk in adults, Canadian study says

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Researchers from the University of Calgary have found a positive connection between the annual flu shot and stroke prevention.

The study, which was published on Wednesday in The Lancet Public Health, examined four million adults from Alberta, of varying ages and health backgrounds, over a 10-year time span.

"We found that those individuals actually had a lower risk of stroke than individuals who didn't receive a flu shot or at other times of the year outside of that six-month-post window," said the study's first author Dr. Jessalyn Holodinsky, a post doctoral fellow at the University of Calgary's Cumming School of Medicine.

The latest research builds on existing knowledge of the connection between influenza and heart disease, and is the largest data set applied to this topic so far.

"[When there is a] peak of influenza in the community, about three or four weeks later we get a peak of stroke admitted to hospital," added Dr. Michael Hill, one of the study's co-authors. "So there's a relationship between upper respiratory infections and vascular events like ischemic-stroke."

Hill further told Global News that this research is "definitive" and will likely lead to more insight in the future.

Although the study did not examine why getting the flu shot lowered the risk of stroke among the participants, it could be because fewer flu cases means less stroke risk. Considering this hypothesis, "vaccination is simply the reason for the reduced cases."

Despite this medical breakthrough, what surprised Holodinsky the most was how strong the "protective effects" are.

"What I was surprised by was the magnitude. I wasn’t surprised that the effect existed but I was surprised by how strong the effect was and especially that the effect existed for all adults," she said, adding that there was a "protective effect regardless of existence of chronic conditions."

While more research is needed, the study's authors believe that getting immunized — along with exercising, not smoking and following a healthy diet — will become general heart health advice.

"I think this is great messaging for the public, especially with influenza vaccination season upon us right now, to go out and consider getting your influenza vaccination," Holodinsky said.

To learn more about the flu shot and when you should get it in Canada, click here.

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