JAMA Network Journals reports that the flu vaccine may be linked to a lower risk of heart attacks for some people, especially those with recent acute coronary syndrome (ACS). According to the authors of the article, researchers are interested in the potential link between respiratory tract infections and ensuing heart events. Their research has revealed a powerful inverse link between flu vaccination and the chance of lethal and non-lethal heart events.

Jacob A. Udell of the University of Toronto worked with his colleagues to examine randomized clinical trials (RCTs) of flu vaccine that studied heart events as efficacy or safety results to identify whether flu vaccination is associated with the hindrance of heart events. Udell and his colleagues found five published and one unpublished RCTs of 6,735 patients that met their criteria for the study.

In the five published RCTs, 95 of 3,328 patients given the flu vaccine developed a significant heart event compared with 151 of 3,231 given a placebo within one year of follow-up. The inclusion of the unpublished data did not change the results.

In an analysis of three RCTs of patients with pre-existing coronary artery disease, the chance of major adverse heart events among patients with a history of recent ACS was a lot lower with flu vaccination compared to patients with stable CAD. Results were not altered by the inclusion of the unpublished data.

“Within this global meta-analysis of RCTs 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,” the authors noted.