Co-administration w/ other vaccines may increase adverse events. Concomitant immunosuppressive therapy or an existing immunodeficiency may affect immunization. False +ve ELISA serologic tests for HIV-1, hepatitis C, & especially HTLV-1 may occur following flu vaccination. Medicinal products to control epilepsy or paroxysmal (phenytoin, carbamazepine, phenobarb), theophylline, warfarin, Ig, immune inhibitory agents (corticosteroid, cyclosporine, anticancer drug, including RT) may cause interaction.