Specific Aim 1. To test the hypothesis that high dose trivalent influenza vaccine will reduce the composite of death or cardiopulmonary events compared with standard dose quadrivalent influenza vaccine in high-risk cardiovascular patients. Patients with recent AMI or HF hospitalization will be randomized to high dose versus standard dose vaccine for up to three influenza seasons. The primary endpoint will be time to first occurrence of death or cardiopulmonary hospitalization within each influenza season. Hospitalizations will be ascertained utilizing multiple approaches (phone, patient report, and electronic health records). Key secondary outcome measures will include total (first and recurrent) cardiopulmonary hospitalizations or death, time to first occurrence of cardiovascular death or cardiopulmonary hospitalization, time to occurrence of all-cause death or cardiopulmonary hospitalization across all enrolled influenza seasons, time to occurrence of all-cause death, and time to first occurrence of cardiopulmonary hospitalizations.