Acute Myocardial Infarction and Influenza
What is the effect of influenza vaccination on incident acute myocardial infarction (AMI) across the entire population?
The purpose of this systematic review of case–control studies is twofold: 1) to estimate the association between influenza infection and AMI, and 2) to estimate the association between influenza vaccination and AMI. Cases included those conducted with first-time AMI or any AMI cases. Studies were appraised for quality, and meta-analyses using random-effects models for the influenza exposures of infection and vaccination were conducted.
A total of 16 studies (8 on influenza vaccination, 10 on influenza infection and AMI) met the eligibility criteria, and were included in the review and meta-analysis. Recent influenza infection, influenza-like illness, or respiratory tract infection was significantly more likely in AMI cases, with a pooled odds ratio [OR] of 2.01 (95% confidence interval [CI], 1.47-2.76). Influenza vaccination was significantly associated with AMI, with a pooled OR of 0.71 (95% CI, 0.56-0.91), equating to an estimated vaccine effectiveness of 29% (95% CI, 9%-44%) against AMI.
The authors concluded that this meta-analysis of case–control studies found a significant association between recent respiratory infection and AMI.
This study reports that influenza infection is significantly associated with AMI, with cases having double the risk of influenza infection or respiratory tract infection compared with controls. Furthermore, the estimated vaccine effectiveness against AMI was comparable with the efficacy of currently accepted therapies for secondary prevention of AMI from clinical trial data. Given the high global burden of AMI, and ischemic heart disease being the leading cause of death and disability in the world, influenza vaccination could be added to other preventive strategies and confer additional population health benefits on AMI prevention since vaccination is inexpensive, safe, and effective.
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