Secondary Prevention with Flu Vaccine
Abstract & Commentary
Synopsis: Influenza vaccination at the time of hospital admission for coronary events or procedures may reduce the rate of subsequent events and death.
Source: Gurfinkel EP, et al. Circulation. 2002;105: 2143-2147.
Epidemiologic studies have shown an increase in myocardial infarction (MI) and cardiovascular death during influenza outbreaks. Thus, Gurfinkel and the FLUVACS study group conducted a randomized, prospective, multicentered, parallel-group controlled, single-blind study of flu vaccine in 200 patients with acute MI within 72 hours and 101 patients for elective percutaneous coronary intervention (PCI) during the winter of 2001 in the Southern Hemisphere. Patients enrolled in the treatment group received a unique flu vaccine against 3 flu strains intramuscularly. Follow-up telephone visits were done at 1 and 6 months. The incidence of cardiovascular death was 2% in the vaccine group and 8% in the controls (P = .01). The triple end point of mortality, MI or rehospitalization for recurrent angina requiring angioplasty or bypass surgery was also lower in the vaccine group—11% vs 23% (P = .009). There was no essential difference in these results when the 2 groups of patients were considered separately. Gurfinkel et al concluded that influenza vaccination at the time of acute MI or elective PCI may reduce the risk of recurrent ischemic events and death for 6 months during the flu season.
Comment by Michael H. Crawford, MD
This interesting report is described by Gurfinkel et al as a pilot trial, but since it was clearly positive, it was the leading clinical report in the May 7, 2002, issue of Circulation. Basic research supports that prevention of viral infections may be beneficial in patients with coronary atherosclerosis. In animal models, viral infections can cause or accelerate atherosclerosis development and this effect can be blocked by vaccination. Also, viral titers have been correlated with restenosis rates after PCI in humans. There are several molecular mechanisms that may explain the atherogenic effects of viral infections including augmented inflammation, alterations in cholesterol metabolism, enhanced oxidation, and changes in the coagulation system. At this time we do not fully understand the molecular basis of these observations.
Although this is a pilot trial, it is hard to argue against recommending a flu shot for everyone with acute MI or undergoing PCI and perhaps everyone with coronary artery disease. They are approved, recommended for the elderly, relatively inexpensive, and fairly safe. So we can add flu shots to the long and growing list of therapeutic agents recommended for secondary prevention. We are truly in the polypharmacy era in cardiovascular care.
Dr. Crawford is Professor of Medicine, Mayo Medical School; Consultant in Cardiovascular Diseases, and Director of Research, Mayo Clinic, Scottsdale, AZ.
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