If avoiding an achy, feverish week or so laid up with the flu doesn’t motivate you to get a flu shot, a new study linking flu shots to a lower incidence of heart disease might persuade you to roll up your sleeve.
People in the study who got flu shots were one-third less likely to have heart issues, such as heart failure or a heart attack, compared to those who opted against vaccination. The flu shot was associated with an even greater reduction of heart problems if someone had heart disease to start with, according to the study.
“This is one further piece of evidence to convince patients to go out and get their flu shot,” said the study’s lead author, Dr. Jacob Udell, a cardiology and clinician scientist, at Women’s College Hospital at the University of Toronto.
Results of the study are published in the Oct. 23/30 issue of the Journal of the American Medical Association.
Past research has suggested a link between the influenza virus — the virus that causes the flu — and an increased risk of heart events. And, conversely, previous research done on the influenza vaccine has suggested an association between the vaccine and a reduced risk of heart issues. But, most of these studies were small and none looked specifically for a heart-protective effect from the influenza vaccine.
The flu vaccine is currently recommended for everyone over 6 months of age in the United States, according to the U.S. Centers for Disease Control and Prevention. The vaccine is highly recommended for certain groups, including people with heart disease.
To get an idea of how well the vaccine might protect against heart events, the researchers reviewed all of the clinical trials done on the influenza vaccine from 1947 through mid-2013.
The investigators included six randomized clinical trials comprising nearly 7,000 people in their analysis. The average age of the study participants was 67, and about half were women. Just over 36 percent had a history of cardiac disease.
The researchers found that those who received an influenza vaccine were 36 percent less likely to have a heart event than those who hadn’t had a vaccine.
When the researchers looked at just the three trials that included people with recent heart disease, they found an even greater potential protective effect. People with recent heart problems who got the flu vaccine were 55 percent less likely to have another event compared to those who didn’t get the vaccine.
The risk of dying from cardiovascular disease was nearly 20 percent lower for those who received the flu vaccine versus those who hadn’t, according to the study.
Udell said this study wasn’t designed to prove that influenza vaccine can lower heart disease risk, but he said that the researchers believe they’ve come close to proving cause and effect without conducting a clinical trial specifically designed to look for a protective effect from the flu vaccine.
“We would like to do a randomized clinical trial so that a skeptical public can put the issue to rest,” Udell said.
The researchers believe that the vaccine protects against heart disease by preventing influenza and its accompanying inflammation. “When you get the flu, the body mounts an inflammatory response. Those aches and pains you feel with the flu are part of the immune response. That inflammation may trigger plaques in the arteries to erupt,” Udell explained.
Dr. Suzanne Steinbaum, a preventive cardiologist at Lenox Hill Hospital, in New York City, agreed that preventing the inflammation associated with the flu is the likely reason that getting a flu vaccine reduces the risk of heart problems.
“People always ask me what they can do for themselves. I say get a flu shot; it will protect your heart, too. This study provides a compelling argument for getting the shot,” Steinbaum said.