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.