A new Canadian study suggests that patients with a history of heart disease who get the flu shot could reduce their risk of a heart attack or stroke by more than half.

The study, published Tuesday in the Journal of the American Medical Association, showed that patients with acute coronary syndrome -- which means they recently had a heart attack or had unstable angina -- had a 36 per cent lower risk of a major cardiovascular event, such as a heart attack, stroke or heart failure, within a year of receiving a seasonal flu vaccine.

Those who specifically suffered a heart attack recently, they had a 55 per cent lower risk of a major cardiac event after receiving the vaccine.

The study reviewed six clinical trials on heart health in people who had received the flu vaccine. The studies included more than 6,700 patients with acute coronary syndrome and who had an average age of 67.

They found that among those who didn't get a flu vaccine or who got a placebo, 4.7 per cent (151 patients) had a major cardiovascular event, such as a heart attack or stroke, within a year. But among the patients who did get the vaccine, only 2.9 per cent (95 people)  had a major cardiovascular event.    

When the researchers looked at patients with pre-existing coronary artery disease and a recent heart attack or unstable angina, the risk of major heart or vascular event was especially lower among those who had the flu vaccine -- 10.3 per cent vs. 23.1 per cent.

"If the flu vaccine can reduce the risk of cardiac events, these shots could have considerable impact on cardiac health," lead researcher Dr. Jacob Udellsaid in a statement.

He and his co-authors note that the flu vaccine is a "low-cost, annual, safe, easily administered, and well-tolerated therapy" and that more study on using it to prevent heart events in those at risk is warranted.

Udell, a cardiologist at Women's College Hospital, and study co-author Dr. Michael Farkouh, director of the University of Toronto's Heart and Stroke Richard Lewar Centre, are currently in the process of organizing a larger clinical trial to follow heart disease patients for up to 12 months after receiving the flu shot.

"These findings are all the ammunition we need to move forward," Farkouh said. "We'll build on this research with a definitive, international trial to conclusively determine whether the flu shot prevents heart attacks." 

As heart disease is the leading cause of death among men and women in North America, the researchers say their study could significantly reduce the burden on the health care system.

"While preventative care involves lifestyle changes and taking your pills, now, we may also be able to tell patients by getting your flu shot, it might save your life," Udell said.