FDA Highlights: Flu vaccine linked to reduction in ensuing cardiovascular events

by Bruce Sylvester – A newly published meta-analysis suggests that influenza vaccination lowers the risk of major adverse cardiovascular events like heart failure or hospitalization for heart attack, and the greatest protective effect appeared among patients with recent acute coronary syndrome (ACS), such as heart attack or unstable angina.

The study was published in the October 23/30 issue of JAMA.

Jacob A. Udell, M.D., M.P.H. of the University of Toronto, and colleagues conducted a meta-analysis of all randomized clinical trials of influenza vaccine which had included evaluation of cardiovascular events among the efficacy or safety outcomes. They sought to identify any correlation between influenza vaccination and prevention of cardiovascular events.

The researchers identified five published and 1 unpublished trials of 6,735 patients (average age of 67 years, 51 percent female, 36 percent with a cardiac history and average follow-up time of 7.9 months) that met inclusion criteria for the meta-analysis. They stratified subjects with and without a history of acute coronary syndrome (ACS) within 1 year of randomization.

In the 5 published trials, 95 of 3,238 subjects who received influenza vaccine (2.9 percent) developed a major adverse cardiovascular event compared with 151 of 3,231 subjects (4.7 percent) treated with placebo or control within 1 year of follow-up. This amounted to an absolute risk difference favoring flu vaccine of 1.74 percent.

Addition of the unpublished data did not significantly change the findings (2.9 percent influenza vaccine vs. 4.6 percent placebo or control).

In a subgroup analysis of 3 trials enrolling subjects with pre-existing coronary artery disease (CAD), risk of major adverse cardiovascular events among subjects with a history of recent ACS was lower with vaccine (10.3 percent influenza vaccine vs. 23.1 percent placebo or control), an absolute-risk difference of 12.9 percent, compared to subjects with stable CAD (6.9 percent influenza vaccine vs. 7.4 percent placebo or control).

Addition of unpublished data did not change the outcomes.

The authors concluded, “Within this global meta-analysis of RCTs [randomized controlled trials] that studied patients with high cardiovascular risk, influenza vaccination was associated with a lower risk of major adverse cardiovascular events within 1 year. Influenza vaccination was particularly associated with cardiovascular prevention in patients with recent ACS. Future research with an adequately powered multicenter trial to confirm the efficacy of this low-cost, annual, safe, easily administered, and well-tolerated therapy to reduce cardiovascular risk beyond current therapies is warranted.”