An important clinical link exists between influenza and cardiovascular disease. While no unequivocal causal relationship has been established between influenza infection and acute MI, influenza is estimated to be responsible for approximately 36,000 deaths and 300,000 hospitalizations annually in the U.S. Childhood and chronic diseases, including cardiovascular disease, in adults are risk factors for poor outcomes during influenza epidemics.
In a 2006 Science Advisory Statement, the American College of Cardiology (ACC) and the American Heart Association, along with seven other professional associations, cited the influenza vaccination as a preventive strategy for patients with cardiovascular disease (J Am Coll Cardiol 2006;48:1498-1502).
The advisory statement noted that the estimated influenza vaccination rate for patients in the U.S. between 18 and 64 years of age with cardiovascular disease is between 35 percent and 40 percent. Additionally, studies of voluntary acceptance of seasonal influenza vaccine among healthcare workers themselves have consistently shown compliance rates of less than 50 percent (Trustee 2011;65:39-40).
The recommendation to administer annual influenza vaccination is designed to promote secondary prevention of cardiovascular events. The strength of evidence for this recommendation is identified as Class I, Level B. The evidence is based on a randomized, controlled trial Flu Vaccination in Acute Coronary Syndromes [FLUVACS], in which 301 hospitalized patients with coronary artery disease were randomized to receive or not to receive influenza vaccinations (Eur Heart J 2004;25:25-31). At the end of one year, the relative risk of cardiovascular death in the vaccinated group was 0.25 compared with the unvaccinated group, and the relative risk of the composite end point of cardiovascular death, non-fatal MI, or severe ischemia was 0.59. At the end of two years, similar magnitude risk reductions were noted, but because of the number of patients lost to follow-up, the statistical significance of the differences was not demonstrable.
Importantly, there is no evidence that influenza vaccination increases the probability of cardiovascular events. In a study of more than 39,000 patients in the U.K., there was no increase in the risk of MI or stroke in vaccinated patients. In this study, the incidence rates for these acute events was lower in the vaccinated cohort at the measurement on day 28; however, these differences disappeared when the results were adjusted for age (J Am Coll Cardiol 2006;481498-1502).
Cardiologists should follow the simple steps below to ensure that all patients are immunized:
- Discuss with patients the importance of immunization for influenza.
- Stock and administer influenza vaccinations in the office or refer to a primary care physician's office or local pharmacy.
- Provide patients with "prescription" recommendation as a reminder to them to obtain an influenza vaccination.
- Place posters or flyers in the office to promote influenza vaccination.
- Influenza vaccine should be administered as soon as supplies become available and should be given through March of each year. In addition, practicing cardiologists, practice office staff and/or hospital staff should be immunized annually for influenza prevention for themselves and their patients.
Dr. Lazarous is associate professor of medicine (cardiology), and Dr. Kumar is professor of medicine and chair of infectious disease at Georgetown University School of Medicine in Washington, D.C. Dr. Oetgen is clinical professor of medicine (cardiology) at Georgetown and is senior vice president of Science and Quality of the ACC.