Influenza vaccine improves cardiovascular outcomes in patients with coronary artery disease: A systematic review and meta-analysis

Background: There are inconsistent data on the clinical benefit of the influenza vaccine on cardiovascular outcomes in patients with coronary artery disease (CAD). Therefore, the aim of our study was to evaluate the effect of the influenza vaccine on cardiovascular outcomes in CAD patients. Methods: We searched four electronic databases from inception to September 21, 2021. Randomized controlled trials (RCTs) assessing the efficacy of influenza vaccine in CAD patients were included. The primary outcome was major adverse cardiovascular events (MACE) and secondary outcomes were all-cause mortality, cardiovascular mortality, and myocardial infarction. The risk of bias was assessed using the Cochrane Risk of Bias 2.0 tool. Effect sizes were expressed as risk ratio (RR) with its 95% confidence interval (CI). All meta-analyses were performed using a random-effects model. Results: Five RCTs involving 4211 patients were included. The mean age ranged from 54.5 to 67 years and 75% of patients were men. Influenza vaccine significantly reduced the risk of MACE (RR, 0.63; 95% CI, 0.51–0.77), all-cause mortality (RR, 058; 95% CI, 0.4–0.84) and cardiovascular mortality (RR, 0.53; 95% CI, 0.38–0.74) compared to control group. The risk of myocardial infarction was similar between both groups (RR, 0.69; 95% CI, 0.47–1.02). The certainty of the evidence was low for MACE, all-cause mortality, and cardiovascular mortality and was very low for myocardial infarction. Conclusions: Our review shows that the influenza vaccine may reduce cardiovascular events in CAD patients. Therefore, we suggest that it be actively applied as part of secondary prevention in this population.