Study of Biomarkers of Immune Activation Associated with Symptoms and Immune Responses After Influenza Vaccination in Adults

Inclusion Criteria: 1. Healthy male or female subjects aged 24-54 years inclusive. (Healthy in the opinion of the investigator, based on medical history and clinical exam, with no active disease process that could interfere with the study endpoints) 2. Has a body Mass Index ≥18 and ≤30 3. Is able to read and understand the Informed Consent Form (ICF), and understand study procedures. 4. The subject has signed the ICF. 5. The subject is available for follow-up for the duration of the study. 6. The subject agrees to abstain from donating blood during their participation in the study, or longer if necessary. 7. If the subject is a heterosexually active female, she is willing to use an effective method of contraception (e.g. oral contraceptive pill; intrauterine device; injectable or implanted contraceptive; physiological or anatomical sterility) from 30 days prior to study vaccination until the end of the study. 8. Willing to undergo urine pregnancy tests prior to vaccination at screening. 9. The subject has venous access sufficient to allow blood sampling as per the protocol. Exclusion Criteria: 1. Pregnant or lactating. 2. Known hypersensitivity to any component of the study vaccine (α-RIX-Tetra®): the active components (vaccine antigens) or any of the excipients (disodium phosphate dodecahydrate, potassium dihydrogen phosphate, magnesium chloride hexahydrate, α-tocopheryl hydrogen succinate, polysorbate 80, octoxinol 10), eggs (chicken proteins, ovalbumin), gentamycin sulphate, formaldehyde, and sodium deoxycholate or those who have had a previous life-threatening reaction to previous influenza vaccinations. 3. History of influenza infection in the past 5 years, defined here as severe respiratory infection with fever (\> 38°C) and preventing normal daily activity during a minimum of 3 days. 4. Vaccination with the 2016/2017 seasonal influenza vaccine and/or any other seasonal influenza vaccine within the preceding 5 influenza seasons (i.e. since season 2011/2012) before the first study visit. 5. Presence of primary or acquired immunodeficiency states with a total lymphocyte count less than 1,200 per mm3 or presenting other evidence of lack of cellular immune competence e.g. leukaemias, lymphomas, blood dyscrasias, or patients receiving immunosuppressive therapy (including use of oral or parenteral corticosteroids in a dose ≥ 5 mg prednisone daily or equivalent within one month prior to visit 1or cytotoxic or immunosuppressive or immunomodulating drugs within 6 months prior to visit 1). 6. Regular use of non-steroidal anti-inflammatory drugs (oral or parenteral route) within 6 months of Visit 1 considered by the study physician as likely to interfere with immune responses. 7. Current intake of excessive amounts of alcohol (≥ 14 units for women and ≥ 21 units for men) and not willing to adapt this use during the study period. 8. Currently performing extreme physical activities (as evaluated by the investigator) and not willing to adapt this activity during the study period. 9. Receipt of a vaccine within 30 days of visit 1, or requirement to receive another vaccine within the study period. 10. Presence of an acute severe febrile illness at time of immunisation. 11. History of alcohol, narcotic, benzodiazepine, rilatine, or other substance abuse or dependence within the 12 months preceding Visit 1. 12. Smoking in the past 6 months OR \> 5 pack-year lifetime history 13. Receipt of blood products or immunoglobulins, or blood donation, within 3 months of study start. 14. Any condition that, in the investigator's opinion, compromises the subject's ability to meet protocol requirements or to complete the study. 15. Currently participating in another clinical study with an investigational or non-investigational drug or device, or has participated in a clinical trial within the 3 months preceding Visit 1. 16. Unable to read and speak Dutch or English to a fluency level adequate for the full comprehension of procedures required in participation and consent.