This week’s post is being published early due to newsworthiness.

by James Hubbard, MD, MPHMedia Checkup: Does the Flu Shot Really Prevent Heart Attacks?

Okay. I know some of you have concerns about whether the flu shot does more harm than good, whether it works, and how well it does (not so great last year for those over 65). In fact, it’s still hit-or-miss on whether the powers that be can guess each year’s flu strains correctly for the vaccine. (Seems to me, though, they have a lot better track record than those guessing on the weather.) But a new study making the media rounds may make you look at the flu shot in a whole different way.

I don’t go into detail about many medical studies on this blog unless they relate to preparing for a disaster or managing medical problems thereafter. But I think this study fits the bill because, as I’ve suggested before, preventing medical problems is one of the best way to medically prepare.

Anyway, a study published this month in The Journal of the American Medical Association showed convincing evidence that taking the flu shot can decrease heart attacks, angina, congestive heart failure, and strokes. To save some writing, let’s just bunch them all together and call them cardiovascular events. It can also decrease the deaths caused from these problems. The study didn’t determine whether the shot itself prevents these problems or avoiding the flu prevents them.

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“Taking flu shot may decrease heart attacks, strokes, etc, by at least 38 percent in following months.”

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Study Details

A group of international scientists led by a Canadian researcher with the University of Toronto looked at all the studies over the past years concerning flu shots and cardiovascular events that occurred after them. They gleaned downed to studies most well done—for instance, the ones with the largest amount of participants and the double-blind ones (meaning neither the doctor nor the patient knew whether they were dealing with a flu shot or placebo)—and they found that people who received the vaccine had significantly fewer cardiovascular events within the following several months to year.

In particular there were 6,735 participants, about equal amounts of men and women. The average age was 67, and 36 percent had known heart disease. The researchers followed them post flu shot for an average of eight months.

Overall:

  • 4.7 percent of people who didn’t get the vaccine had a cardiovascular event during the time they were followed.
  • 2.9 percent of people who got the vaccine had a cardiovascular event.

That’s a 38 percent decrease in cardiovascular events in those who had the shot.

The results were even more dramatic in those who had a heart attack or case of angina (chest pain coming from decreased blood flow to the heart) within one year prior to the shot. In this group:

  • 23.1 percent who didn’t get the vaccine had an acute cardiovascular event within the time studied.
  • 10.25 percent of those who got the flu shot had such an event.

That’s a 55.8 percent reduction in cardiovascular event among those who had had a recent heart attack or angina.

Overall 1.7 percent who didn’t have the flu shot died from any cause, versus 1.3 percent who had it. That’s a 23.5 decrease.

What the Flu Shot Has to Do With Your Heart

In the study I was surprised not to come across how many flu cases the vaccine prevented. Since it’s well-known that getting the flu increases your risk of a heart attack or angina (the flu indirectly affects your heart vessels), I presume the scientists are assuming that decreased flu cases were the reason for the decrease in cardiovascular events.

And I presume they didn’t rule in or out the idea that part of the reason could also have been the vaccine-prompted boost in the body’s immune system.

Study Weaknesses

One weakness is that even though the researchers picked the studies they thought were done the best, none were perfect. Then, they used their statistical wizardry (which is, in fact, an amazing science) to determine their findings.

The most reliable way to know if their findings are true is to have, in fact, another study specifically designed to target the question, does the flu shot help prevent heart attacks and other cardiovascular events?

In the end, this is just some added information for you to digest, especially if you or a loved one has cardiovascular disease. Always check with your regular doctor for individual advice.

Also check out some of my past blog posts on the flu and the flu shot.

What’s your take? Does this new information persuade you to get the shot, or are you going to depend on other preventive measures only? Have you known anyone who got the flu followed by heart problems or a stroke?