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Does the flu shot curb heart disease?

By Alexandra Sifferlin,
updated 1:11 PM EDT, Tue October 30, 2012
The influenza vaccine may reduce the risk of heart related disease and death by up to 50%, researchers say.
The influenza vaccine may reduce the risk of heart related disease and death by up to 50%, researchers say.
  • Studies: The flu shot may reduce the risk of heart-related disease and death by 50%
  • The shots may prevent bouts of flu that aggravate unstable plaques in the heart
  • Larger-scale studies are needed to confirm the findings, researchers say

( -- Here's something to consider if you haven't gotten your flu shot: people who are vaccinated may have a lower risk of heart disease.

In two separate studies presented at the Canadian Cardiovascular Congress, researchers say the influenza vaccine may reduce the risk of heart related disease and death by up to 50%. That supports current recommendations that people at high risk for flu-related complications, including people with heart disease, get vaccinated. H1N1 vaccines linked to Guillain-Barre syndrome but not birth defects

In one of the studies, lead study author Dr. Jacob Udell, a cardiologist at Women's College Hospital and the University of Toronto and his research team reviewed four studies involving flu vaccines and heart health.

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The studies included 3,227 participants, half of whom had confirmed heart disease. Half of the participants received the influenza vaccine and half were inoculated with a placebo. Tamiflu made my kid hallucinate. I think the flu is preferable to delirium

After one year, those who received the flu vaccine had a 50% reduced risk of suffering major cardiac events like heart attack and stroke and a 40% reduced risk of heart-related death.

"These findings support current guideline recommendations that patients with heart disease or risk factors for heart disease should get an annual flu shot, with now an additional potential benefit," says Udell, who says he hopes the findings encourage more people to get immunized.

"If reproducible, these findings suggest an annual flu vaccine with minimal risk may have a dramatic ability to reduce our risk of cardiovascular disease. Hopefully this is one additional reason to get your flu shot this year."

In the second study, cardiologists from Sunnybrook Health Sciences Centre in Toronto looked at the role of flu vaccines among patients with implantable cardiac defibrillators (ICD), battery-operated implants that electrically stimulate the heart for those whose organs are failing. Traditionally, doctors have known that patients tend to need more ICD shocks during flu season, so study author Dr. Ramanan Kumareswaran wanted to investigate ways of reducing this need to rely on the device.

Study: Why flu hits some people harder than others

The researchers focused on 230 patients between the ages 70 to 74 who came in for appointments related to their ICD care at Sunnybrook Health Sciences Centre from September through November 2011. They filled out questionnaires about their demographics, health status and whether they received a flu vaccine in the past year. Seventy-eight percent of the participants had received the vaccine and 20% had not in the previous year.

On average, those who opted out of the vaccine had more ICD therapies overall. A little over 13.5% of these patients experienced at least one ICD therapy during the flu season compared to the 10.6% of patients who got the vaccine.

"What is interesting is that if this is consistent over time, it could be of significant benefit to our patient population who already have compromised survival to start with," wrote Dr. Sheldon Singh, one of the study's authors.

Although it's not clear how the flu vaccine protects the heart, it's possible that the shots prevent bouts of flu that drive up inflammation and immune responses that could aggravate unstable plaques in the heart. In fighting off influenza, for example, the body's immune system often revs up inflammatory reactions that can lead to blood clots or trigger rupture of plaques that then cause heart attacks. Exposure to common chemicals may weaken vaccine response

Researchers from both studies say larger-scale studies are needed to support their findings, but Dr. Beth Abramson from Canada's Heart and Stroke Foundation said in a statement that both studies support the country's recommendations that patients at high risk of developing flu complications like those with heart disease and diabetes receive the vaccine.

The American Heart Association urges everyone ages six months and older receive the flu vaccine. It's especially important for those who may transmit the flu to high risk individuals such as children, seniors, pregnant women, people with disabilities, people with health conditions and those who travel abroad to get vaccinated. Roll up your sleeves.

This story was initially published on

Does the flu shot curb heart disease?

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