Every August, primary care doctors stock their clinics with influenza vaccines and start reminding patients to get their annual shot. We usually tell patients, “The flu vaccine can reduce your risk of severe illness during the upcoming respiratory virus season.” While that’s true and important, there’s another important reason to get vaccinated: reducing your risk of a heart attack.

Doctors have long recognized that people are more likely to have a heart attack or stroke in the days or weeks after certain infections, especially those that affect the lungs, like influenza. There are three ways in which influenza is thought to trigger cardiovascular events.

First, after infection, the body mounts a rapid, powerful immune response that includes a surge of inflammatory chemicals and clotting factors. If your arteries have any fatty deposits (known as “plaques”) in their walls, inflammation can destabilize the plaques, clots can form at those rupture points, and blood flow to part of the heart can be blocked.

Second, studies in mice and tissue cultures show that influenza can directly infect the cells that line blood vessels, disrupt their normal function, and persist in arterial plaques.

Finally, influenza raises heart rate, increases oxygen demand, and can lower blood pressure. All of these can stress an already weakened cardiovascular system.

These combined effects are part of........

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