As we head into influenza season, we are likely steeling our nerves for the inevitable debate with some of our patients about receiving the influenza vaccination.

We are used to hearing patients say, “I have never had it, and I have never gotten the flu,” or (my favorite), “Last time I got the shot, I got the flu.” Arguments that – while defying chance, logic, and science in general – keep us rooted in the daily joys of clinical practice.

Some handy influenza facts:

1. In well-matched years, the number needed to treat (NNT) to prevent one flu-like illness is 33.

2. In unmatched years, the NNT is 100.

We should be adding to this discussion some information about the observed association between the influenza vaccine and acute myocardial infarction (AMI). If compelling arguments about preventing flu-like symptoms don’t carry the day, maybe preventing heart attack will.

Dr. Michelle Barnes and her colleagues at UNSW Australia, Sydney, published the results of a systematic review of case-control studies evaluating the association between the influenza vaccine and AMI (Heart, 2015 Aug. 26. doi:10.1136/heartjnl-2015-307691 ). In this study, the investigators identified 16 studies on AMI and influenza vaccination or influenza infection.

The odds of influenza infection, influenza-like illness, or respiratory infection were significantly greater in patients with AMI (odds ratio, 2.01; 95% confidence interval: 1.47-2.76). Influenza vaccine was associated with a lower risk of AMI (OR, 0.71; 95% CI: 0.56-0.91).

This is the first meta-analysis compiling all case-control data on the relationship between AMI and the influenza vaccine. Overall, cases had double the risk of influenza or respiratory tract infection, compared with controls.

Influenza has been hypothesized to cause coronary artery occlusion through stenosis of subcritical atherosclerotic plaque, and it has been shown to promote atherogenesis in animal models. The connection between AMI and influenza was first observed in the 1930s during the flu season.

But medicine has a short memory, and our patients sometimes do as well. So, it is time we remind them about this link and encourage them to get their flu shots.

Dr. Ebbert is professor of medicine, a general internist at the Mayo Clinic in Rochester, Minn., and a diplomate of the American Board of Addiction Medicine. The opinions expressed are those of the author and do not necessarily represent the views and opinions of the Mayo Clinic. The opinions expressed in this article should not be used to diagnose or treat any medical condition nor should they be used as a substitute for medical advice from a qualified, board-certified practicing clinician. Dr. Ebbert has no relevant financial disclosures about this article. Follow him on Twitter @jonebbert .

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