The flu shot might just prevent a heart attack

A study just published in the Journal of the American Medical Association (JAMA) shows that patients who had received influenza vaccine had a lower risk of cardiovascular problems.

This study is a meta-analysis that reviewed data from several other previously done studies. (Udell, JA et al., JAMA. 2013;310(16):1711-1720. doi:10.1001/jama.2013.279206)

It has been known that patients who have had a recent case of the flu are at higher risk of having a cardiovascular event, like a fatal or non-fatal heart attack. The reason(s) for this is unclear. It is not known if a recent case of the flu predisposes you to plaque rupture in a coronary artery causing a heart attack, or whether it produces heart failure, or causes arrhythmias, or some other mechanism is involved.

Heart via Shutterstock

Heart via Shutterstock.

This study was not investigating the cause of the cardiac event, but rather, whether a recent influenza vaccination lowered the risk of a cardiovascular event. They defined a cardiovascular event as: hospitalization for a heart attack, fatal heart attack, heart failure, unstable angina or the need for a rapid coronary revascularization (e.g., heart catheterization, stenting), among others.

There were over 6,500 patients studied in all. Some had a previous cardiac history (like a heart attack), while others had no record of any cardiovascular disease. They were a mixture of men and women, with an average age in the mid-60s.

After review and analysis, the information shows that there is a decreased risk for cardiovascular events for people who receive influenza vaccine.

As the authors state:

“[I]nfluenza vaccination was associated with a lower risk of major adverse cardiovascular events within 1 year. Influenza vaccination was particularly associated with cardiovascular prevention in patients with recent ACS [Acute Coronary Syndrome]. Future research with an adequately powered multicenter trial to confirm the efficacy of this low-cost, annual, safe, easily administered, and well-tolerated therapy to reduce cardiovascular risk beyond current therapies is warranted.”

Even though each of the six studies from which the data for the meta-analysis was taken differed somewhat in their designs, the authors say:

“Still, despite differences in trial designs, risk of bias, sample size, cardiovascular risk of participants, circulating influenza activity, vaccination strategy, duration of follow-up, and number of observed events, our meta-analysis demonstrated a consistent association between influenza vaccination and a lower risk of cardiovascular events.”

This study supports earlier studies that suggested similar findings. And influenza vaccination has been recommended for several years as a means to possibly lower the risk of heart attacks.

More research is needed, specifically a study to look at exactly that question: Does preventing influenza by means of a vaccine directly cause a decrease in cardiovascular events.

However, since influenza vaccination is already recommended virtually universally, this just adds another reason why flu shots are a good idea.

Mark Thoma, MD, is a physician who did his residency in internal medicine. Mark has a long history of social activism, and was an early technogeek, and science junkie, after evolving through his nerd phase. Favorite quote: “The most exciting phrase to hear in science... is not 'Eureka!' (I found it!) but 'That's funny.'” - Isaac Asimov

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