Immune Response to High-Dose vs. Standard Dose Influenza Vaccine

This 5-year proposal is a randomized study of split-virus influenza vaccine (SVV) in a high-dose (HD) vs. standard-dose (SD) formulation in each of five influenza seasons to define the key determinants of vaccine-mediated protection against influenza and how these immunologic mediators may be enhanced by vaccination with a newly approved high-dose influenza vaccine in older people

Inclusion Criteria: 1. Written informed consent provided by the participant 2. Age 20-40 years old with no underlying chronic diseases or age ≥65 years old 3. Willing to receive influenza vaccination 4. Older cohort has received their influenza vaccine for the previous influenza season \- Exclusion Criteria: 1. Immunosuppressive disorders or medications (including oral prednisone in doses \>10 mg daily) 2. Have not received influenza vaccination in the past or cannot be vaccinated due to previous severe reaction to influenza vaccine, egg, latex, or thimerosol allergies, or refusal of vaccination 3. Participant has received a community available influenza vaccine for the approaching influenza season 4. Females who are pregnant at Visit 1 (a pregnancy test will be administered for all females of child-bearing potential) \-