An increasing body of evidence suggests that getting vaccinated for the flu may lower the risk of stroke. In the latest study, published in Neurology in September 2022, researchers looked at a health care database of almost 3 million people in Spain over a 14-year period and identified 14,322 people who were at least 40 years old and had experienced one ischemic stroke (caused by blocked blood flow to the brain). They also selected 71,610 control subjects whose demographics matched the stroke survivors.
In this group of 85,932 people, 41.4 percent of the stroke survivors and 40.5 percent of the control subjects had been vaccinated for the flu. Those who'd been vaccinated were more likely to be older and have risk factors for stroke such as high blood pressure and high cholesterol. After adjusting for these factors, the study authors found that people who received a flu shot were 10 to 15 percent less likely to have a first stroke than those who did not get the vaccine, regardless of sex, age, and risk profile.
This study was observational only; it did not test whether a flu vaccine protects against having a stroke. It just showed an association between the flu vaccine and a reduction in stroke, but the finding provides yet another reason to get vaccinated. Influenza can cause severe illness and has been associated with an increased risk of stroke.
How a flu shot could prevent strokes isn't entirely clear, but the benefit reported in the Neurology study wasn't just during flu season. This may mean the flu vaccine prevents or reduces inflammation, a risk factor for stroke and cardiovascular disease. Inflammation can be caused or worsened by bacteria or a virus, excessive alcohol consumption, obesity, inactivity, chronic stress, and smoking.
People are often advised to get vaccinated in September or October, but flu season peaks in January and February in the United States, and cases are usually reported well into spring. If you haven't scheduled a flu shot yet, it's not too late. Find out if your doctor or pharmacist is still administering shots or check the U.S. Centers for Disease Control and Prevention's vaccine locator.
People ages 65 and older are at higher risk of developing serious flu complications for two reasons. They often are more likely to have underlying chronic conditions—such as diabetes, heart disease, and chronic obstructive pulmonary disease— and immune response to infections diminishes with age. Because of that, older people should request a high-dose vaccine. If one isn't in stock, they should, for at least some protection, take what's available.
Dr. Elkind is professor of neurology and epidemiology at Columbia University in NewYork City and chief clinical science officer at the American Heart Association.
