There was no statistically significant difference in vaccine effectiveness against the composite of all-cause death, myocardial infarction, or stent thrombosis between early (HR 0.69) and late (HR 0.74) season influenza vaccination (P=0.848 for interaction).
RCT (n=2,532)
Double-blind
1:1 permuted block design stratified by trial site
Yes
Does early versus late influenza vaccination improve the composite of all-cause death, MI, or stent thrombosis in patients with acute myocardial infarction?
There is no statistically significant difference in cardiovascular benefit between early and late season influenza vaccination in patients with acute myocardial infarction, supporting vaccination regardless of timing.
Hazard Ratio: 0.69 (95% CI 0.45–1.07)
Absolute Event Rate: 6% vs 8.4%
Absolute Risk Reduction: 2.4%
p-value: p=0.848 for interaction
Influenza vaccination reduces the risk of adverse cardiovascular events.The IAMI trial randomly assigned 2571 patients with acute myocardial infarction (AMI) to receive influenza vaccine or saline placebo during their index hospital admission. It was conducted at 30 centers in 8 countries from October 1, 2016 to March 1, 2020. In this post-hoc exploratory sub-study, we compare the trial outcomes in patients receiving early season vaccination (n = 1188) and late season vaccination (n = 1344).The primary endpoint wasthe composite of all-cause death, myocardial infarction (MI), or stent thrombosis at 12 months. Thecumulative incidence of the primary and key secondary endpoints by randomized treatment and early or late vaccination was estimated using the Kaplan-Meier method. In the early vaccinated group, the primary composite endpoint occurred in 36 participants (6.0%) assigned to influenza vaccine and 49 (8.4%) assigned to placebo (HR 0.69; 95% CI 0.45 to 1.07), compared to 31 participants (4.7%) assigned to influenza vaccine and 42 (6.2%) assigned to placebo (HR 0.74; 95% CI 0.47 to 1.18) in the late vaccinated group (P = 0.848 for interaction on HR scale at 1 year). We observed similar estimates for the key secondary endpoints of all-cause death and CV death. There was no statistically significant difference in vaccine effectiveness against adverse cardiovascular events by timing of vaccination. The effect of vaccination on all-cause death at one year was more pronounced in the group receiving early vaccination (HR 0.50; 95% CI, 0.29 to 0.86) compared late vaccination group (HR 0.75; 35% CI, 0.40 to 1.40) but there was no statistically significant difference between these groups (Interaction P = 0.335). In conclusion,there is insufficient evidence from the trial to establish whether there is a difference in efficacy between early and late vaccinationbut regardless of vaccination timing we strongly recommend influenza vaccination in all patients with cardiovascular diseases.
Akhtar et al. (Wed,) conducted a rct in Acute myocardial infarction (AMI) (n=2,532). Influenza vaccination vs. Placebo (0.9% normal saline) was evaluated on Composite of all-cause death, myocardial infarction (MI), or stent thrombosis at 12 months (HR 0.69, 95% CI 0.45 to 1.07, p=0.848 for interaction). There was no statistically significant difference in vaccine effectiveness against the composite of all-cause death, myocardial infarction, or stent thrombosis between early (HR 0.69) and late (HR 0.74) season influenza vaccination (P=0.848 for interaction).