We seem always to be looking for health benefits from things that might otherwise be seen as “guilty pleasures,” such as red wine, coffee, and chocolate. And we also look for additional health benefits from things we do for a specific reason. A high-fiber diet, for example, may not only help keep you “regular” (don’t you love our euphemisms for digestive functions?) but may also help lower cholesterol and reduce your risk of colon cancer.

So it comes as no surprise that medical scientists are investigating whether influenza vaccination may be good for something besides making you less likely to get influenza. They probably think we need extra motivation, because many of us don’t take the flu that seriously, and we’re not keen on getting shots. Maybe if we think it’s good for more than just protection from the flu, we’ll be more likely to go for it.

In this instance, Canadian researchers in cardiology have found that vaccination seems to have beneficial cardiovascular effects: specifically, a substantial reduction in the likelihood of heart attack, stroke, or death from cardiovascular causes. The study was reported by Dr. J.A. Udell and colleagues at the Canadian Cardiovascular Conference 2012 (Canadian Journal of Cardiology Vol. 28, Issue 5, Supplement, Page S161)

When I started reading an article in a popular news outlet describing this research, I thought it was an association that could have any number of possible causes. We see so many studies of that sort. Scientists look at people with various health problems and see that those who got a particular intervention (like a vaccine) had fewer bad things happen to them. Then the question is always whether it was the intervention of interest that conferred the benefit, or just that people who received that intervention were receiving regular medical care of all sorts, and who knows what, among all the things done for them, was really responsible. Even when you try to adjust for differences in all of those other things, you can still be missing possibly responsible influences you didn’t think of.

But this study was not reporting an association in search of a possible cause-and-effect relationship. These investigators took a population of patients (with a reasonable sample size) and randomized them to influenza vaccine or placebo. That’s the kind of study it takes to see whether the one thing you’re interested in is responsible for observed differences in outcomes. If the sample size is large enough, and the patients are randomized to one intervention or another, or intervention versus placebo, all of the other factors that might cause different results for the two groups of patients should be very similar, thus isolating the one difference you’re studying.

The results, as reported, are pretty striking: a 50% reduction in heart attack or stroke and a 40% reduction in mortality. And those results seemed to apply to patients both with and without previously diagnosed cardiovascular disease.

If this is real, the question is why? There have been many studies over the years looking at the relationship between infection and inflammation and bad things happening in blood vessels. Some studies have suggested that patients who’d been treated, for one reason or another, with certain kinds of antibiotics over the years seemed to have fewer heart attacks. Researchers guessed that certain infections might predispose to inflammation, and subsequent development of vessel-narrowing plaque, in coronary arteries.

The U.S. Centers for Disease Control and Prevention is telling us everyone should get the flu vaccine every year. Many of us are not listening. I am in the camp of the skeptics, as I am in relation to just about everything. I want to see evidence that the vaccine substantially lowers my statistical likelihood not just of getting influenza but of becoming seriously ill with influenza, and that the magnitude of this benefit greatly exceeds the magnitude of the risk of a serious adverse reaction to the vaccine. Over the years I have found the evidence of such a favorable risk-benefit calculation to be reasonably convincing for older folks and those with chronic diseases (heart and lung diseases and diabetes), but not so convincing for younger and otherwise healthy people.

And I’ve been less than impressed with the scientific evidence that all health care workers should get the vaccine to keep from spreading the flu from their infected patients to others who are susceptible. It makes sense, but the evidence that it really works that way just isn’t compelling. So I get my flu shot to keep my employer happy, but I remain skeptical.

But the idea of other benefits has definite appeal. I often take ibuprofen for various aches and pains. The fact that there is a little bit of suggestive evidence that it reduces the likelihood of developing Alzheimer’s disease suits me just fine. If I’m going to do it anyway, an unexpected benefit is welcome. Now, that is an example of an association that may or may not have causality. No one has done a randomized, placebo-controlled study and followed patients long term, which is what you’d have to do, because that’s a disease that develops over a period of many years.

In this case, however, the causality may be real, because the study was done in such a way as to figure that out. Notice I say it may be real. Why am I still skeptical? Well, to begin with, I haven’t read all the details of the study. I read a report in the popular press of the presentation of the study’s results at a medical meeting in Toronto. I don’t know if the study has been accepted for publication in a reputable, peer-reviewed medical journal. Once that happens, if it does, I’ll be able to read the paper and draw firm conclusions about its results. Many papers are presented at meetings and never get published. And many papers that get published don’t really prove what the authors think or say they do. And then, of course, any important scientific study should be reproducible – meaning if other scientists conduct another study in the same way, they should get similar results. Reproducibility is essential to credibility in scientific investigation.

So all I can say right now is that this is very intriguing, and if it turns out to be real, we will all have another reason to get the influenza vaccine each year.

Dr. Solomon teaches emergency medicine to the residents at Allegheny General Hospital in Pittsburgh and is Medical Editor in Chief of ACEP News. He is a social critic and political pundit and blogs at www.bobsolomon.blogspot.com.