Can a flu shot really lower your risk for a heart attack?

A study published Monday in the Canadian Medical Association Journal offered an enticing possibility: that something as simple as a flu shot cold help prevent recipients from suffering a heart attack. From a public health perspective, the news might boost the ranks of patients getting vaccinated against influenza. And from a liability standpoint, physicians stand to see a decline in the leading diagnosis linked to malpractice suits.

For the study, British researchers compared the medical records of 16,012 first-time heart attack victims ages 40 and older with the records of nearly 62,700 people who had not had heart attacks. After factoring other major risks for heart attacks, such as smoking and family history of heart ailments, the research found that the flu shot was associated to a 19 percent reduction in the rate of first heart attack, the study found.

What's more, early vaccination for flu--between September and mid-November--was associated with a 21 percent reduction in the rate of heart attacks compared with vaccination after mid-November, which was associated with a 12 percent reduction.

However, study authors, including Niro Siriwardena, a professor at the University of Lincoln in England, acknowledge that the study does not prove that flu shots prevent heart attacks, but only that vaccination is associated with a reduction in cases.

According to the University of Minnesota's Center for Disease Research and Policy, however, two other researchers who were asked to comment on the study called it plainly flawed, chiefly because the authors did not conduct separate assessments of the effects of vaccination on heart attack risk during flu season and at other times of the year. According to the critics, separate analyses are needed to determine the extent of the "healthy user effect"--the tendency for healthier individuals to get vaccinated in the first place.

To learn more:
- read the CNN article
- see the story from CBC News
- check out this piece from CIDRAP