Immunogenicity and Safety of the Seasonal Flu Vaccine in Elderly and in SOT Recipients

Elderly: Inclusion Criteria: * Age ≥65 year old. * Able to give informed consent. * Necessity to receive influenza seasonal vaccination in 2013-2015. * Availability for the duration of the study and willingness to attend all scheduled visits. * Hemoglobin value ≥100 g/l , Leukocytes ≥3.5 G/L, Platelets count ≥100 G/l at the time of screening, or determined within 8 weeks before screening in the course of regular medical examination and validated by the medical doctor. Solid-organ transplant recipients Inclusion criteria Age ≥18 year old Solid organ transplantation \>3 months before vaccination Stable patient followed at the outpatient clinic of the Transplantation Center Able to give informed consent. Necessity to receive influenza seasonal vaccination. Availability for the duration of the study and willingness to attend all scheduled visits. Exclusion criteria Previous life-threatening reaction to influenza vaccine (i.e. Guillain-Barre Syndrome) Ongoing therapy for rejection Febrile illness in the past two weeks Exclusion Criteria: * Contraindication against seasonal flu vaccination. * Use of any investigational or non-registered drug or vaccine within 30 days preceding the first dose of the study vaccine, or planned use during the study period and safety follow-up. * Immunodeficiency or chronic administration (defined as more than 14 consecutive days) of immunosuppressive or other immune-modifying drugs within six months prior to the first vaccine dose. (For corticosteroids, this will mean prednisone, or equivalent, ≥0.5 mg/kg/day. Inhaled and topical steroids are allowed). * Hypersensitivity to the active substances, to any of the excipients, to eggs, chicken proteins, neomycin, formaldehyde and octoxinol 9. * Acute disease at the time of enrollment \[Acute disease is defined as the presence of a moderate or severe illness with or without fever. All vaccines can be administered to persons with a minor illness such as diarrhea, mild upper respiratory infection with or without low-grade febrile illness, i.e., temperature \<38°C\]. * An unstable chronic condition (unstable chronic renal failure, unstable diabetes, unstable chronic cardiac condition, uncontrolled asthma, etc.). * Receipt of blood-derived products (immunoglobulin; plasma) within 120 days prior to enrollment.