Influenza Vaccination Associated with Reduced Risk of Major Adverse Cardiovascular Events: Meta-Analysis

With the goal of determining if seasonal influenza vaccination is associated with prevention of cardiovascular events, Canadian investigators conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) available on MEDLINE (1947 – August 2013), EMBASE (1947 – August 2013) and the Cochrane Library Central Register of Controlled Trials (inception – August 2013) that examined major cardiovascular event experience in high-risk patients given influenza vaccine, placebo or no treatment. Analyses were stratified by subgroups of patients with and without a history of acute coronary syndrome (ACS) within one year of randomization.

Five published and one unpublished RCTs of a total of 6,735 patients (mean age 67 years; 51.3 percent female; 36.2 percent with a cardiac history; mean follow-up time 7.9 months) were included in the meta-analysis. Influenza vaccine administration was associated with a lower risk of composite cardiovascular events (2.9 percent vs. 4.7 percent; RR 0.64; 95 percent CI, 0.48 – 0.86; P = 0.003) in the five published trials. A treatment interaction was detected between patients with (RR 0.45 [95 percent CI, 0.32 – 0.63]) and without (RR 0.94 [95 percent CI, 0.55 – 1.61]) recent ACS. Results remained similar with the addition of unpublished data.

The study authors concluded that the use of influenza vaccine was associated with a lower risk of major adverse cardiovascular events. The greatest treatment effect was seen among the highest-risk patients with more active coronary disease.