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Association Between Influenza Vaccination and Cardiovascular Outcomes in High-Risk Patients


Among nontraditional cardiovascular risk factors, recent influenza-like infection is associated with fatal and nonfatal atherothrombotic events. As a result, a study published in the Journal of the American Medical Association (2013;310:1711-1720) was performed to determine if influenza vaccination is associated with prevention of cardiovascular events.


For the study, a systematic review and meta-analysis was performed studies reported in MEDLINE (1946-August 2013), EMBASE (1947-August 2013), and the Cochrane Library Central Register of Controlled Trials (inception-August 2013). Studies included randomized clinical trials (RCTs) comparing influenza vaccine vs. placebo or control in patients at high risk of cardiovascular disease that also reported cardiovascular outcomes either as efficacy or safety events.


Two investigators extracted data independently on trial design, baseline characteristics, outcomes, and safety events from published manuscripts and unpublished supplemental data. High-quality studies were considered those that described an appropriate method of randomization, allocation concealment, blinding, and completeness of follow-up.


Five published and 1 unpublished randomized clinical trials of 6,735 patients (mean age, 67 years; 51.3% women; 36.2% with a cardiac history; mean follow-up time, 7.9 months) were included. Influenza vaccine was associated with a lower risk of composite cardiovascular events (2.9% vs 4.7%; P = .003) in published trials. A treatment interaction was detected between patients with and without recent acute coronary syndrome (ACS) (P for interaction = .02).


The authors concluded that based on a meta-analysis of RCTs, the use of influenza vaccine was associated with a lower risk of major adverse cardiovascular events with the greatest treatment effect seen among the highest-risk patients with more active coronary disease. The authors suggested that a large, adequately powered, multicenter trial is warranted to address these findings and assess individual cardiovascular end points.


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