Patients hospitalized for acute cardiac conditions-including acute myocardial infarction, acute heart failure, pulmonary embolism, arrhythmias, and hypertensive emergencies-represent a heterogeneous population at very high risk of recurrent cardiovascular events. Influenza infection may act as a trigger for adverse cardiovascular events. Given the persistently low influenza vaccination uptake despite evidence-based benefits observed in vulnerable populations, including patients with cardiac conditions, new strategies to improve vaccination coverage are being explored. Recently, increasing attention has been directed toward an approach already used in fields such as neonatology, where vaccinations are administered prior to hospital discharge.

In this investigator-initiated, single-center, randomized, open-label interventional study, we will evaluate whether influenza vaccination administered within 24 hours before hospital discharge in patients hospitalized for acute cardiac conditions is safe and effective in reducing subsequent infections, cardiovascular events, and mortality during the 6 months following hospitalization.

Inclusion Criteria:

• Acute cardiac hospitalization,
• Planned discharge home within the next 48 hours following completion of in-hospital treatment,
• No prior influenza vaccination for the current influenza season.

Exclusion Criteria:

• History of a severe adverse reaction to influenza vaccination,
• Allergy to any component of the vaccine to be administered,
• Discharge to another hospital for continuation of treatment or discharge to a long-term care facility,
• Antibiotic therapy to be continued after discharge.