Studies on the immunological response of immunocompromised patients (e.g., transplant, HIV, oncology, chronic renal failure, SLE) to the influenza vaccine have demonstrated that some of these patients develop antibody titers at a protective level within 4-6 weeks. However, the titers were decreased compared to healthy controls, especially if the immunocompromised patients were on immunosuppressive agents. The frequency of influenza in immunocompromised patients was lower after immunization and there were almost no major side effects from the vaccine.