October 23rd, 2013

Flu Vaccine May Help Prevent Cardiovascular Events

A new meta-analysis published in JAMA offers the best evidence yet that the flu vaccine may help prevent cardiovascular events.

Jacob Udell and colleagues analyzed data from five published clinical trials in which 6469 patients were randomized to flu vaccination or placebo (or no treatment). People who received the flu vaccine were significantly less likely than controls to have a cardiovascular event (2.9% vs. 4.7%; RR 0.64, CI 0.48-0.86, p = 0.003). The protective effect was largely restricted to people who had had a recent acute coronary syndrome (ACS):

  • RR for patients with recent ACS: 0.45 (CI 0.32-0.63)
  • RR for patients without recent ACS: 0.94 (CI 0.55-1.61; P for interaction = 0.02).

Results were similar after inclusion of unpublished data. The authors calculated that 58 people would need to be vaccinated to prevent 1 major cardiovascular event.

The authors wrote that if their findings are correct, wider use of the flu vaccine could have a significant impact on cardiovascular disease:

If severe influenza-associated morbidity and mortality is in part due to acutely triggered ischemic cardiovascular events, and a vaccine preventing influenza could decrease the risk of cardiovascular events, then this therapy could address a sizable component of residual cardiovascular risk not addressed by current therapy and provide yearlong coverage through 1 simple inoculation.

They recommended that “an adequately powered multicenter trial” be performed “to confirm the efficacy of this low-cost, annual, safe, easily administered, and well-tolerated therapy.”

In an accompanying editorial, Kathleen Neuzil writes that more than half of people under the age of 65, and as many as one third of those over 65, don’t receive annual flu vaccines. She points out that “one of the most consistent and relevant findings of operational research is that recommendation for vaccination from physicians and other health care professionals is a strong predictor of vaccine acceptance and receipt among patients… all health care practitioners can recommend influenza vaccine to their patients.”

In an interview with JAMA reporter Mike Mitka, Udell said that the study offers “yet another reason why receiving influenza vaccine might be a beneficial thing to do. And those hospitalized with a heart attack should be vaccinated before they walk out the door so they don’t have care gaps that could be very dangerous.”

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