Flu Shots Linked to Lower Heart Attack Risk

A new study finds that older people who get the flu shot are 19 percent less likely to have a heart attack.

Getting a flu shot can help prevent influenza. But now, a large study in Britain indicates that older adults who get an annual flu vaccination are less likely to suffer a heart attack.

The study involved more than 78,000 people, age 40 and older.

"Our research suggests that flu shots are associated with a reduction in relative risk of heart attack in adults by about 19 percent," says  Niroshan Siriwardena, a researcher at Britain's University of Lincoln who led the study.
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The reduction was even higher - 21 percent - for people who got their vaccination early in the flu season.

The results were mathematically adjusted to reflect the fact that people who are at higher risk for heart attack in the first place are more likely to get a flu shot.  

Although Siriwardena is careful to point out that his study is one of associations, not necessarily cause-and-effect, he does offer one possible link between the seemingly unrelated conditions of influenza and heart attack.

"The key theory is that [in] coronary arteries which are narrowed, that influenza causes an inflammatory process, which makes the plaques more liable to rupture," says Siriwardena. "So flu is encouraging plaque rupture and triggering off a heart attack. That's the theory."

For a lot of people, the message of this study is that now there's one more reason to get a flu vaccination. But Siriwardena the scientist has a slightly different analysis.

"The take-home message of this study is really that we need to do further research to look at this link between flu and heart attack to see whether there's a real cause-and-effect here."

The study by Niroshan Siriwardena and colleagues is published in the Canadian Medical Association Journal.