Acute myocardial infarction and influenza: a meta-analysis of case–control studies

• Published in: Heart (British Cardiac Society) Vol. 101; no. 21; pp. 1738 - 1747
• Main Authors: Barnes, Michelle, Heywood, Anita E, Mahimbo, Abela, Rahman, Bayzid, Newall, Anthony T, Macintyre, C Raina
• Format: Journal Article
• Language: English
• Published: England BMJ Publishing Group LTD 01.11.2015; BMJ Publishing Group
• Series: Original article
• Subjects: Bias; Cardiac Risk Factors and Prevention; Cardiovascular disease; Case-Control Studies; Heart attacks; Humans; Immunization; Influenza Vaccines - therapeutic use; Influenza, Human - complications; Influenza, Human - prevention & control; Myocardial Infarction - etiology; Myocardial Infarction - prevention & control; Outcome Assessment (Health Care); Preventive Medicine - methods; Preventive Medicine - statistics & numerical data; Risk Assessment; Studies; Vaccines
• DOI: 10.1136/heartjnl-2015-307691
• ISSN: 1355-6037

ObjectiveAcute myocardial infarction (AMI) is the leading cause of death and disability globally. There is increasing evidence from observational studies that influenza infection is associated with AMI. In patients with known coronary disease, influenza vaccination is associated with a lower risk of cardiovascular events. However, the effect of influenza vaccination on incident AMI across the entire population is less well established.MethodThe purpose of our 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.Results16 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 OR 2.01 (95% CI 1.47 to 2.76). Influenza vaccination was significantly associated with AMI, with a pooled OR of 0.71 (95% CI 0.56 to 0.91), equating to an estimated vaccine effectiveness of 29% (95% CI 9% to 44%) against AMI.ConclusionsOur meta-analysis of case–control studies found a significant association between recent respiratory infection and AMI. The estimated vaccine effectiveness against AMI was comparable with the efficacy of currently accepted therapies for secondary prevention of AMI from clinical trial data. A large-scale randomised controlled trial is needed to provide robust evidence of the protective effect of influenza vaccination on AMI, including as primary prevention.