Flu shots may reduce risk of heart trouble

Compilation of clinical trials finds consistent results

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LOS ANGELES — Get a flu shot to ward off a case of influenza, and as an added bonus you'll reduce your risk of a heart attack, stroke or other unpleasant "cardiovascular event," a new study finds.

For some time, researchers have suspected that flu shots can protect heart health as well as respiratory health. They have tested this theory in a handful of clinical trials, and the results have been mixed.

Now an international group of researchers has compiled data from a dozen peer-reviewed randomized clinical trials to see if they could get a clearer answer to the question. What they found was "a consistent association between influenza vaccination and a lower risk of cardiovascular events," according to their report in Wednesday's edition of the Journal of the American Medical Association.

Five of the trials the team examined compared a flu vaccine to a placebo vaccine or other type of control. In those trials, 3,238 patients got a real vaccine and 95 of them — 2.9 percent — went on to experience "a major adverse cardiovascular event," the JAMA report said. For the sake of comparison, 3,231 patients in those trials got a placebo or control and 151 of them — or 4.7 percent — later had a cardiovascular event, according to the study.

That translates into a 36 percent reduced risk of a serious heart problem simply by getting a flu shot — something everyone over the age of 6 months should be doing anyway. Based on these figures, the researchers calculated that one death or serious illness due to heart trouble could be prevented by vaccinating 58 additional people.

Experts aren't sure why the flu increases the risk of serious heart problems, but they have their theories. It may cause a plaque that has built up inside the arteries to rupture, or it may cause the heart muscle to become inflamed, among other possibilities. Knowing what's going on inside the body would help figure out who would get an extra boost from a flu shot, and why.