The goal of this randomized, double-blind, placebo-controlled clinical trial is to investigate the immunological effects of influenza vaccination outside of the influenza season on arterial inflammation in patients with a recent acute myocardial infarction (AMI). The primary objective is to compare the effects of influenza vaccination to those of a placebo in reducing post-myocardial infarction coronary inflammation as measured by coronary computed tomography angiography (CCTA). The main questions it aims to answer are:

Does influenza vaccination reduce arterial inflammation as measured by CCTA at week 8 after percutaneous coronary intervention (PCI) in comparison to baseline? Does influenza vaccination modulate systemic inflammation as measured by blood biomarkers and in-vitro challenge tests at week 8 after PCI in comparison to baseline? Researchers will compare the effects of influenza vaccination with those of a placebo.

Following informed consent patients are randomized in a 1:1 fashion to influenza vaccination or placebo up to 7 days following PCI. Blood tests for immune cell phenotyping and transcriptomic and proteomic analyses will be collected at baseline and 8 weeks after study inclusion. Patients will undergo CTCA at baseline (≤ 7 days of an AMI) and 8 weeks after PCI.

Inclusion Criteria:

• Patients with a diagnosis of non-ST-segment elevation myocardial infarction
• A finalized coronary PCI
• Male or non-fertile female subjects ≥18 years. (Females without childbearing potential, postmenopausal women and women with a history of hysterectomy or other medical conditions that preclude pregnancy)
• Written informed consent
• A CCTA can be scheduled within 7 days after PCI

Exclusion Criteria:

• Has received influenza vaccination within 6 months
• Other vaccination planned within 8 weeks (including covid-19 booster doses)
• Severe allergy to eggs or previous allergic reaction to influenza vaccine
• Cardiac surgery or staged PCI planned within 8 weeks
• Coronary stent involving the proximal RCA
• Suspicion of febrile illness or acute, ongoing infection
• Hypersensitivity to the active substances or ingredients of Vaxigrip or against any residues, such as eggs (ovalbumin or chicken proteins), neomycin, formaldehyde and octoxinol
• Subjects with endogenic or iatrogenic immunosuppression that may result in reduced immunization response
• Inability to provide informed consent
• Previous randomization in the ELIMINATE trial
• Any non-cardiovascular condition, e.g. malignancy, with a life expectancy of less than 1 year based on the investigator´s clinical judgement.
• Contraindication to coronary CT angiography (e.g., inability to lie flat, contraindication to glyceryl trinitrate, previous contrast allergy or contrast-induced nephropathy, severe renal impairment [eGFR <30 mL/min/1.73 m2])
• Atrial fibrillation
• Uncontrolled chronic inflammatory disease
• Unable to comply with protocol requirements