Immune Response to Seasonal Influenza Vaccine in HIV Infected Individuals

This is a study to establish the immunologic response in HIV-seropositive individuals to the FDA approved seasonal influenza vaccine when it is available. HIV-seropositive individuals seen in the Infectious Diseases Clinic at George Washington University, Medical Faculty Associates and receive this vaccination, on label, as part of standard of care will be invited to participate. The study will require a 10-ml sample of whole blood to be drawn from each participant prior to the dose of the seasonal influenza vaccine and at 3 weeks after the vaccine dose and at 3 months after the vaccine dose. No additional samples are envisioned. Serum will be separated and will frozen and stored in the Clinical Trials Unit until all patient samples have been obtained. At that time the antibody levels to the vaccine antigens will be measured. Data that will be collected from the subject's medical record includes the following: * Age, gender, race * CD4 count * HIV viral load * History of prior influenza immunization including the 2009-2010 trivalent vaccine * HIV antiviral medication history Data that will be collected from the subject during participation in study * Antibody levels prior to vaccination * Dose date of the seasonal influenza vaccination * Antibody levels 3 weeks after the vaccination