INVESTED is a multi-site trial comparing high-dose (60 μg per vaccine viral strain) trivalent influenza vaccine to standard-dose (15 μg per viral strain) quadrivalent influenza vaccination for up to three influenza seasons in high-risk cardiovascular disease patients with a history of myocardial infarction in the previous 12 months OR history of heart failure hospitalization in the previous 24 months. Subjects will be randomly assigned to receive either the high-dose or standard-dose vaccine.