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ESC Congress 2021: Results from the largest trial of its kind suggest that flu vaccination should be part of in-hospital treatment after myocardial infarction.
Influenza vaccination early after a myocardial infarction (MI) or in high-risk coronary artery disease (CAD) reduces the risk of all-cause mortality, MI, or stent thrombosis at 12 months compared to placebo, according to new research presented on August 30 at the European Society of Cardiology (ESC) Congress 2021.
“The IAMI trial found that in patients with myocardial infarction or high-risk coronary disease, early influenza vaccination resulted in a lower risk of the composite of all-cause death, myocardial infarction or stent thrombosis at 12 months compared with placebo. Our findings suggest that influenza vaccination should be considered as part of in-hospital treatment after myocardial infarction,” said principal investigator Ole Fröbert, MD, PhD, adjunct professor, consultant cardiologist, Örebro University Hospital, Sweden, in an ESC press release.
The IAMI trial was the largest randomized trial to date to evaluate if influenza vaccination improves outcomes following MI or percutaneous coronary intervention in high-risk patients with CAD. The study was conducted at 30 hospitals in 8 countries over 4 influenza seasons between October 2016 and February 2020.
Participants were randomized in a 1:1 ratio to receive either the influenza vaccine or placebo within 72 hours of an invasive coronary procedure or hospitalization. The primary endpoint was a composite of all-cause death, MI, or stent thrombosis at 12 months. Researchers used a hierarchical testing strategy for the secondary outcomes of all-cause death, cardiovascular death, MI, and stent thrombosis, according to the study.
Researchers aimed to enroll 4400 patients, but because of the COVID-19 pandemic, the data safety monitoring board stopped the trial after 2571 patients (58% of the target) were enrolled in April 2020. The average age of participants was 60 years and 18% were women.
During the 12-month follow-up, the primary outcome occurred in 67 participants (5.3%) in the vaccine group and 91 (7.2%) in the placebo group (hazard ratio [HR] 0.72; 95% confidence interval [CI], 0.52-0.99; p=0.040).
Death from any cause occurred in 37 patients (2.9%) in the vaccine group and 61 (4.9%) in the placebo group (HR 0.59; 95% CI, 0.39-0.89; p=0.010), and rates of cardiovascular death were 2.7% and 4.5%, respectively (HR 0.59; 95% CI, 0.39-0.90; p=0.014).
There was no difference between the cohorts in the rate of MI, which occurred in 25 participants (2%) in the vaccine group and 29 patients (2.4%) in the placebo group (HR 0.86; 95% CI, 0.50-1.46; p=0.57), according to the study.
“Despite being guideline-recommended influenza vaccination is underutilized and the findings from this study emphasize the importance of seasonal influenza vaccination in patients with cardiovascular disease,” concluded study authors.
Researchers reported that serious adverse events were rare and of similar type and incidence in both groups. With that said, injection site reactions such as pain, redness, swelling, and hardening were reported significantly more often in participants in the vaccine group.
Reference: Fröbert O, Götberg M, Erlinge D, et al. Influenza vaccination after myocardial infarction: A randomized, double-blind, placebo-controlled, multicenter trial. Circulation. In press.