Study leader Dr. Jacob Udell, a cardiologist at Women's College Hospital and clinician-scientist at the University of Toronto, said the influenza vaccine's heart protective effects might be even greater among those who receive a more potent vaccine.
"Our study provides solid evidence that the flu shot helps prevent heart disease in vulnerable patients -- with the best protection in the highest risk patients," Udell said in a statement. "These findings are extraordinary given the potential for this vaccine to serve as yearly preventative therapy for patients with heart disease, the leading cause of death among men and women in North America."
Udell and Dr. Michael Farkouh of the Peter Munk Cardiac Centre at the University Health Network reviewed six clinical trials on heart health in people who received the flu vaccine that involved more than 6,700 patients with a history of heart disease.
The study, published in the Journal of the American Medical Association, found people who received the flu shot:
-- Had a 36 percent lower risk of a major cardiac event such as a heart attack, stroke, heart failure, or death from cardiac-related causes one year later.
-- Had a 55 percent lower risk of a major cardiac event if they had a recent heart attack.
-- Were less likely to die from cardiac-related and other causes.
-- Were less likely to have a major cardiac event with a more potent vaccine compared with the standard seasonal vaccine.
"If the flu vaccine can reduce the risk of cardiac events, these shots could have considerable impact on cardiac health," Udell said.
However, the researchers cautioned that a large prospective clinical trial is necessary to confirm the effectiveness and safety of the influenza vaccine as a therapy that will reduce the risk of heart attack or stroke in people with heart disease.