Influenza Vaccination and Cardiovascular Risk
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An updated meta-analysis examining the association between influenza vaccination and CV events that incorporates a recently published clinical trial in patients with recent acute coronary syndrome (ACS). Clinical trials published between 2000 and 2021 that randomized participants (outpatients or inpatients) to either influenza vaccine or placebo/control were included. Subgroup analysis was performed examining the association in stable outpatients and those who had a recent ACS. The primary outcome was a composite of CV death or hospitalization for myocardial infarction, unstable angina, stroke, heart failure, or urgent coronary revascularization within 12 months of vaccination. The secondary outcome was CV mortality.
Six published randomized controlled trials comprising a total of 9,001 patients were included (mean age, 65.5 years; 42.5% women; 52.3% with a cardiac history), of whom 4,510 received the influenza vaccine (2,890 in intramuscular form, 1,620 in intranasal form). Overall, influenza vaccine was associated with a lower risk of composite CV events (3.6% vs. 5.4%; relative risk [RR], 0.66; 95% confidence interval [CI], 0.53-0.83; p < 0.001). The association was significant only in patients with recent ACS (RR, 0.55; 95% CI, 0.41-0.75), and not stable outpatients (RR, 1.00; 95% CI, 0.68-1.47) (p for interacti Findings were similar for CV mortality.

Influenza vaccination is overall associated with lower CV events, with a notably significant effect of 45% lower risk in individuals with recent ACS.