Reviwer : Dr. Gökay Taylan

Name of the Study: Influenza Vaccination after Myocardial Infarction: Randomized Trial- IAMI

Published Congress: ESC 2021

Link: https://www.ahajournals.org/doi/abs/10.1161/CIRCULATIONAHA.121.057042

Background:

During influenza epidemics, deaths from cardiovascular diseasIe occur at a higher rate comparing  with non-epidemic periods. Observational and small randomized studies suggest that the influenza vaccine may reduce future cardiovascular events in patients with cardiovascular disease. Flu vaccines are recommended for patients with heart disease but are not part of standard hospital care following an acute myocardial infarction (MI). The IAMI trial is the largest randomized trial to evaluate whether influenza vaccination following a percutaneous intervention in patients with recent MI or high-risk coronary artery disease (CAD) improves outcomes.

Objective:

The purpose of this study is to evaluate the impact of influenza vaccination may reduce the combined incidence of death, MI, and stent thrombosis in patients with recent MI or high-risk CAD.

Methods:

The IAMI study is a randomized, placebo-controlled, double-blind, multicenter study. Due to the Covid-19 pandemic, the data safety and monitoring board decided to halt the trial before attaining the prespecified sample size. Between October 1, 2016, and March 1, 2020, 6696 patients from 30 centers across eight countries were screened, and 2571 participants were randomized to the study.1290 patients were categorized to influenza vaccine group and 1281 patients to the placebo group. Here, saline placebo or inactivated influenza vaccine were administered to patients with recent MI (99.7% of patients) or high-risk CAD (0.3%). It was administered intramuscularly within 72 hours of an invasive coronary procedure or hospitalization.
The primary composite endpoint consisted of all-cause death, MI, or stent thrombosis at 12 months. A hierarchical testing strategy was used for the key secondary endpoints, including all-cause death, cardiovascular death, MI, and stent thrombosis.

Results:

The mean age of the participants was 59.9±11.2 years, and 18.2% of the study population were female. In addition, 1348 patients (54.5%) were admitted with STEMI, 1119 patients (45.2%) with non-STEMI, and eight patients(0.3%) with stable coronary artery disease. A total of 1868 participants (74.3%) were treated with PCI, and 587 patients (23.4%) received medical treatment only.
During 12-month follow-up period, the primary outcome occurred in 67 participants (5.3%) in influenza vaccine group and 91 participants (7.2%) in placebo group (hazard ratio, 0.72; 95% confidence interval, 0.52 to 0.99; P=0.040). Rates of all-cause death were 2.9% and 4.9% (hazard ratio, 0.59; CI 0.39 to 0.89; P=0.010), of cardiovascular death 2.7% and 4.5%, (hazard ratio, 0.59; CI 0.39 to 0.90; P=0.014), and of MI 2.0% and 2.4% (hazard ratio, 0.86; CI 0.50 to 1.46, P=0.57) in the influenza vaccine and placebo groups, respectively.

Conclusion:

Influenza vaccination of patients with early MI or high-risk coronary heart disease resulted in a lower risk of composite events, all-cause death, and cardiovascular death at 12 months compared with placebo.

Interpretations:

These findings suggest that influenza vaccination should be considered as part of in-hospital treatment after myocardial infarction. Despite being guideline-recommended, influenza vaccination is underappreciated, and the findings from this study emphasize the importance of seasonal influenza vaccination in patients with cardiovascular disease.