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Study links flu vaccine to reduced risk of heart attack, stroke in people at risk

Oct. 23, 2013

A flu shot may do more than protect you from a bout of flu. It may also help protect your heart, especially if you’ve recently had a heart attack or angina.

New research links flu vaccine to lower risk of major cardiovascular events (such as stroke, heart failure or being hospitalized for a heart attack) in high-risk patients. The link was strongest in people with acute coronary syndrome (ACS, which includes conditions such as heart attack or unstable angina). ACS patients who got the flu vaccine had less than half the risk of a major cardiovascular event within the next year, compared to unvaccinated ACS patients.

The study authors determined that for every eight ACS patients who get a flu shot, one heart attack or stroke may be prevented.

Getting the flu is a risk factor for cardiovascular events, but researchers haven't been sure whether having a flu shot can help prevent these incidents. A new study evaluated the relationship between flu vaccine and heart problems by systematically reviewing and analyzing existing research on flu vaccine and cardiovascular events in people with heart risks. The research team was led by Dr. Jacob Udell, a cardiologist at Women’s College Hospital, and included researchers from the University of Toronto as well as international collaborators.

The researchers looked at six randomized controlled trials that included more than 6,700 people in total. About half of those people were women, and the average age was 67. More than one-third of participants had a history of cardiac illness.

In the group as a whole, people who got the flu vaccine were about one-third less likely to have a cardiovascular event within a year compared to those who didn’t get the vaccine. The vaccinated group had a 36 per cent lower risk. The researchers calculated that giving 58 flu shots in this group may prevent one major cardiovascular event.

The researchers also did a separate analysis of the three trials involving people who had coronary artery disease (CAD). In this smaller group, they found that flu vaccine was linked to the greatest drop in cardiac risk among CAD patients who had recent ACS. In the ACS patients, risk of a cardiac event was halved in those who got the flu vaccine, compared to those who didn’t: the risk was 55 per cent lower in the vaccinated group. The results suggest that vaccinating eight ACS patients could prevent one stroke, heart attack or heart failure.

In CAD patients without ACS – whose CAD was stable – there was no significant difference in risk of cardiac events in those who got flu vaccine and those who did not.

These promising results highlight the need for a large trial looking more closely at the link between flu vaccine and heart risks, the study authors write. Dr. Udell and his fellow researchers note that flu vaccine is safe, inexpensive and easy to administer. If further research confirms that it also reduces risk of cardiac events, flu vaccine could have a valuable role in preventive strategies.

The study was published in JAMA on Oct. 23, 2013.

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  • A publication of:
  • Women's College Hospital