Use of the influenza vaccine, particularly among high-risk patients with acute coronary syndrome, is linked to lower risks of major adverse cardiovascular events, according to new findings published in the Journal of the American Medical Association.

"The researchers point out that a large, adequately powered, multicenter trial is warranted to address the findings, and of course that is important, but in the interim, for your high risk cardiac patients - make sure they have had the flu vaccine," said Peter Block, MD, FACC.

A meta-analysis of randomized clinical trials comparing influenza vaccination versus placebo or control in patients with cardiovascular disease found a lower rate of subsequent cardiovascular events associated with vaccination (2.9 percent versus 4.7 percent, RR=0.64, p=0.003). Patients with recent acute coronary syndrome showed the greatest treatment effect (RR=0.45 p=0.02) compared to no influenza vaccination.

"In our meta-analysis of 6735 patients with varying degrees of cardiovascular risk, influenza vaccination was associated with a significantly lower risk of major adverse cardiovascular event," the study authors said. "The risk associated with influenza vaccination was robust, with a greater association seen among patients with recent ACS compared with patients with stable CAD."

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According to lead author Jacob Udell, MD, MPH, Women’s College Research Institute, University of Toronto, Canada, the "influenza vaccination may prevent cardiovascular events via avoidance of atherosclerotic plaque rupture or other forms of cardiac injury in a vulnerable patient and represents a simple, once-annual protective therapy to reduce cardiovascular events."

However, he and the other study authors note that "future research with an adequately powered multicenter trial to confirm the efficacy of this low-cost, annual, safe, easily administered, and well-tolerated therapy to reduce cardiovascular risk beyond current therapies is warranted."

Broader findings could have major implications for health policy and clinical practice. Influenza vaccination is recommended for all individuals over the age of six months and specifically recommended for cardiovascular patients. But vaccine uptake is less than one-third in the general North American population and less than one-half of high-risk populations. Increasing influenza vaccination could address a sizeable component of cardiovascular risk that is not treated by current therapy using a safe and familiar vaccine.

"Regardless of whether influenza vaccine reduces cardiovascular disease, the known morbidity of influenza in older adults with and without high-risk conditions and the known efficacy of the vaccine warrant its use," said Kathleen Neuzil, MD, MPH, Vaccine Access and Delivery, PATH, Seattle, in an accompanying editorial. "All health care practitioners can recommend influenza vaccination to their patients."

Keywords: Health Policy, Acute Coronary Syndrome, Plaque, Atherosclerotic, Influenza Vaccines, Morbidity, Cardiovascular Diseases, Risk Factors, Vaccination

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