Influenza Vaccination After Myocardial Infarction - IAMI

Contribution To Literature:

The IAMI trial showed that influenza vaccination within 72 hours of angiography/PCI/hospitalization among patients with recent MI or high-risk coronary heart disease resulted in a salutary effect on CV outcomes at 12 months compared with placebo, including a lower risk of all-cause and CV mortality.

Description:

The goal of the trial was to assess the safety and efficacy of influenza vaccination among patients with recent myocardial infarction (MI) or high-risk coronary disease.

Study Design

Patients with recent MI or percutaneous coronary intervention (PCI) were randomized in a 1:1 double-blind fashion to either influenza vaccination (n = 1,272) or saline placebo (n = 1,260). The trial was conducted across eight countries and was halted early due to the COVID-19 pandemic on March 1, 2020. The trial medication was administered within 72 hours of coronary angiography/PCI (or hospital admission for centers in Bangladesh). Influenza vaccine content was consistent with World Health Organization (WHO) recommendations according to season and hemisphere.

  • Total screened: 6,696
  • Total number of enrollees: 2,532
  • Duration of follow-up: 12 months
  • Mean patient age: 60 years
  • Percentage female: 18.2%

Inclusion criteria:

  • Age ≥18 years
  • ST-segment elevation myocardial infarction (STEMI) or non-STEMI (NSTEMI) with completed coronary angiography or PCI
  • Patients with stable coronary artery disease (CAD) >75 years of age with additional risk factors

Exclusion criteria:

  • Receipt of influenza vaccination
  • Intention to be vaccinated during the ongoing influenza season
  • Severe allergy to eggs or previous allergic reaction to influenza vaccine
  • Febrile illness or acute, ongoing infection
  • Endogenic or iatrogenic immunosuppression

Other salient features/characteristics:

  • 35.5% current smokers
  • 54.5% with STEMI, 45.2% with non-STEMI, 0.3% with stable CAD
  • 74.3% treated with PCI
  • Crossover from placebo to vaccine arm over course of trial: 13.2%

Principal Findings:

The primary outcome, a composite of all-cause death, MI, or stent thrombosis, for influenza vaccination versus placebo, was 5.3% vs. 7.2% (hazard ratio 0.72, 95% confidence interval 0.52-0.99, p = 0.04).

Secondary outcomes for influenza vaccination vs. placebo:

  • All-cause death: 2.9% vs. 4.9% (p = 0.01)
  • Cardiovascular (CV) death: 2.7% vs. 4.5% (p = 0.014)
  • MI: 2.0% vs. 2.4% (p = 0.57)

Interpretation:

The results of this trial indicate that influenza vaccination within 72 hours of angiography/PCI/hospitalization among patients with recent MI or high-risk coronary heart disease resulted in a salutary effect on CV outcomes at 12 months compared with placebo, including a lower risk of all-cause and CV mortality. It is important to note that the study was terminated prematurely due to the COVID-19 pandemic with approximately 60% of planned enrollment. In addition, approximately 13% crossed over from the placebo arm to the vaccination arm over the course of follow-up. Both of these factors would have biased the results towards null. Therefore, the observed findings are even more impressive.

These findings are consistent with previous studies showing positive effects of influenza vaccination among patients with coronary heart disease. The authors speculate that the mechanism underpinning these findings may be from possible anti-inflammatory effects from vaccination and/or prevention of acute influenza infection, which can trigger CV events. Interestingly, MI rates were not different between the two arms, although CV death was lower with vaccination. These study findings support in-hospital vaccination for influenza after MI to prevent all-cause and CV death and will likely influence future guidelines on this topic.

References:

Frøbert O, Götberg M, Erlinge D, et al. Influenza Vaccination After Myocardial Infarction: A Randomized, Double-Blind, Placebo-Controlled, Multicenter Trial. Circulation 2021;Aug 30:[Epub ahead of print].

Presented by Dr. Ole Frøbert at the European Society of Cardiology Virtual Congress, August 30, 2021.

Clinical Topics: Acute Coronary Syndromes, Cardiovascular Care Team, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Prevention, Stable Ischemic Heart Disease, Vascular Medicine, Interventions and ACS, Interventions and Imaging, Interventions and Vascular Medicine, Angiography, Nuclear Imaging, Chronic Angina

Keywords: ESC Congress, ESC21, Acute Coronary Syndrome, Coronary Angiography, Coronary Disease, COVID-19, Influenza Vaccines, Influenza, Human, Myocardial Infarction, Percutaneous Coronary Intervention, Risk Factors, Secondary Prevention, ST Elevation Myocardial Infarction, Stents, Thrombosis, Vaccination


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