10/23/2013 03:56 pm ET Updated Oct 30, 2013

Flu Shot Could Lower Risk Of Major Heart Events, Review Finds


Getting your flu shot may not just protect you from a week of sniffles, sneezes and misery -- a new review of studies shows it could actually have a protective effect against major heart-related events, such as being hospitalized because of a heart attack.

Researchers from the University of Toronto found that people who were vaccinated against influenza were less likely to have a major heart event, compared with those who weren't vaccinated. The findings are based on a review of five published randomized clinical trials, as well as one unpublished randomized clinical trial. The trials, which all focused on flu vaccinations and heart events, included a total of 6,735 people with an average age of 67 who were followed for an average 7.9 months. A little more than a third of the people had a history of heart problems prior to the trials.

Among the entire group, 2.9 percent of people who got their flu shots had a major negative heart event within one year of follow-up, compared with 4.7 percent of people who didn't get their flu shots (who were in the placebo/control groups in their specific studies). Among those who had recently suffered a heart attack, researchers found that they seemed to especially benefit from the protective effect of the flu shot.

But why does being protected from the flu seem to affect heart health?

"Although acute influenza infection is an independent risk factor for fatal and nonfatal cardiovascular events, the mechanism underlying that risk is less clear," researchers explained in the study. They suggested that a flu infection could trigger a vascular rupture, set off an arrhythmia, lead to heart failure due to fluid overload or even overwhelm the natural defenses of an already "frail and vulnerable patient."

The study was published in the Journal of the American Medical Association.

Previously, a Heart study showed that flu vaccination could help people who have not yet had a major heart event, but are at risk for one. Australia, U.K. and U.S. researchers found that for middle-aged people with narrowed arteries, getting a flu shot cuts heart attack risk in half.


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