If you haven’t gotten your annual flu shot, here’s some powerful motivation: Adults who are immunized against seasonal influenza have a 46% lower risk for fatal or nonfatal heart attacks, strokes and other major cardiovascular (CV) events over the subsequent 12 months, compared to those who received a placebo shot or no shot, according to a recent Harvard analysis that pooled results from randomized clinical trials involving nearly 7,000 men and women.
Another recent study found that people who get their shot early in the flu season, which begins in October, have an even greater reduction in heart-attack-and-stroke risk than those who wait until mid-November to get immunized. Why is influenza vaccination such a powerful weapon against CV events? Here’s a look at the latest research and the facts about flu shots.
Is there any scientific proof linking flu to higher risk for heart attacks and stroke?
Many studies have shown that acute influenza infection is a strong, independent risk factor for heart attacks and strokes. Researchers report that up to 91,000 Americans die each year from CV events triggered by flu. These grim statistics have prompted the American Heart Association and the American College of Cardiology to issue guidelines recommending flu shots for people with cardiovascular disease (CVD).
How does flu contribute to cardiovascular events?
The likely culprit is inflammation, the immune system’s response to infection, in which SWAT teams of white blood cell components are mobilized to battle the invading pathogens. Although this response is normally protective, it can raise heart-attack-and-stroke risk in people with CVD.
To picture how flu could ignite a heart attack or stroke in someone with CVD, think of plaque in the arteries as kindling. Inflammation, which has been shown in recent studies to actually cause CVD, lights the match, causing plaque to rupture explosively through the arterial wall. When a plaque rupture tears the blood-vessel lining, the body tries to heal the injury by forming a blood clot. If the clot blocks a coronary artery, it could spark a heart attack, while a clot that travels to the brain could ignite a stroke.
Who should get a flu shot? The Centers for Disease Control (CDC) recommends vaccination for everyone, except babies under 6 months of age, but cautions that some patients should check with their medical providers before being immunized, including people with a severe allergy to chicken eggs, those who have had a severe reaction to a flu shot, and people who are ill with a fever (they should wait until they recover before getting vaccinated).