title: Ischaemic heart disease, influenza and influenza vaccination: a prospective case control study.
abstract: BACKGROUND
  Abundant, indirect epidemiological evidence indicates that influenza contributes to all-cause mortality and cardiovascular hospitalisations with studies showing increases in acute myocardial infarction (AMI) and death during the influenza season.
  
  
  OBJECTIVE
  To investigate whether influenza is a significant and unrecognised underlying precipitant of AMI.
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  Tertiary referral hospital in Sydney, Australia, during 2008 to 2010.
  
  
  METHODS
  Cases were inpatients with AMI and controls were outpatients without AMI at a hospital in Sydney, Australia.
  
  
  METHODS
  Primary outcome was laboratory evidence of influenza. Secondary outcome was baseline self-reported acute respiratory tract infection.
  
  
  RESULTS
  Of 559 participants, 34/275 (12.4%) cases and 19/284 (6.7%) controls had influenza (OR 1.97, 95% CI 1.09 to 3.54); half were vaccinated. None were recognised as having influenza during their clinical encounter. After adjustment, influenza infection was no longer a significant predictor of recent AMI. However, influenza vaccination was significantly protective (OR 0.55, 95% CI 0.35 to 0.85), with a vaccine effectiveness of 45% (95% CI 15% to 65%).
  
  
  CONCLUSIONS
  Recent influenza infection was an unrecognised comorbidity in almost 10% of hospital patients. Influenza did not predict AMI, but vaccination was significantly protective but underused. The potential population health impact of influenza vaccination, particularly in the age group 50-64 years, who are at risk for AMI but not targeted for vaccination, should be further explored. Our data should inform vaccination policy and cardiologists should be aware of missed opportunities to vaccinate individuals with ischaemic heart disease against influenza.
authors: School of Public Health and Community Medicine, UNSW Medicine, the University of New South Wales, , Sydney, New South Wales, Australia.
authors: C Raina
authors: CR
authors: Macintyre
authors: Anita E
authors: AE
authors: Heywood
authors: Pramesh
authors: P
authors: Kovoor
authors: Iman
authors: I
authors: Ridda
authors: Holly
authors: H
authors: Seale
authors: Timothy
authors: T
authors: Tan
authors: Zhanhai
authors: Z
authors: Gao
authors: Anthea L
authors: AL
authors: Katelaris
authors: Ho Wai Derrick
authors: HW
authors: Siu
authors: Vincent
authors: V
authors: Lo
authors: Richard
authors: R
authors: Lindley
authors: Dominic E
authors: DE
authors: Dwyer
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D009980:Influenza A virus / Q000276:immunology*; D007252:Influenza Vaccines / Q000627:therapeutic use*; D007251:Influenza, Human / Q000150:complications* / Q000453:epidemiology / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000453:epidemiology* / Q000209:etiology; D009517:New South Wales / Q000453:epidemiology; D011379:Prognosis; D011446:Prospective Studies; D015996:Survival Rate / Q000639:trends; D014611:Vaccination
chemical_list: D007252:Influenza Vaccines
keywords: Coronary Artery Disease; Infection
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