Evidence supporting the use of influenza vaccine in patients at risk for coronary artery events largely comes from observational studies or small randomized trials (RCTs). In this study, the authors conducted a systematic review of 6 RCTs (5 published, 1 unpublished) comparing influenza vaccine to placebo on the rate of a composite of major adverse cardiovascular events (i.e. cardiovascular death or hospitalization for myocardial infarction, unstable angina, stroke, heart failure, or urgent coronary revascularization). The 5 published trials showed a pooled risk ratio (RR) of 0.64 (95% confidence interval [CI] 0.48 – 0.86; p<.003), translating to a number needed to treat of 58 to prevent 1 MACE. In these studies, the vaccine appeared more beneficial in patients with recent acute coronary syndromes (RR 0.45; 95% CI 0.32 – 0.63) compared to those with stable CAD (RR 0.94; 95% CI 0.55 – 1.61; p for interaction =.02). There was no association between receipt of influenza vaccine and cardiovascular mortality (pooled RR 0.81; 95% CI 0.3-1.83) or all-cause mortality (pooled RR 0.85; 95% CI 0.45-1.61). Addition of unpublished data did not change the results.

Conclusions:

Influenza vaccination is associated with a reduced risk for major adverse cardiovascular events, particularly among patients with a recent coronary event. This may signify a readily addressable component of residual risk in patients with coronary disease.

• Udell JA, Zawi R, Bhatt DL, Keshtkar-Jahromi M, Gaughran F, Phrommintikul A, Ciszewski A, Vakili H, Hoffman EB, Farkouh ME, Cannon CP. Association between influenza vaccination and cardiovascular outcomes in high-risk patients: A meta-analysis. JAMA. 2013;310:1711-1720