Inclusion Criteria:
* Able to speak and read English
* Male or Female, 65 years and older by date of enrollment
* Weight of 110 lbs or greater
* Has received influenza vaccine in the past seasons without severe adverse reactions
* Willing to receive an FDA-approved age-appropriate and CDC-recommended influenza vaccine for each of the 2022-23, 2023-24, and 2024-25 influenza seasons
* Willing to withhold all other vaccinations 2 weeks prior and 2 weeks after flu vaccination for the 2022-23, 2023-24, and 2024-25 influenza seasons
* Willing and available to participate in 19 study visits over three years around influenza vaccination
* Willing to provide blood samples at sixteen visits over three years
* Willing to agree to genomic testing of samples and sharing of de-identified genomic data generated from samples at the conclusion of the research
Exclusion Criteria:
* Received any vaccine (shingles, pneumococcal, COVID, etc.) within 2 weeks of anticipated flu vaccination for the 2022-23, 2023-24, and 2024-25 influenza seasons.
* Has already received an influenza vaccine for the approaching influenza season (2022-23)
* Has known allergy to eggs or any component of the flu vaccine. \[Although the Advisory Committee on Immunization Practices (ACIP) has concluded that a history of anaphylactic/anaphylactoid or severe allergic reaction to eggs should no longer be considered a contraindication to vaccination with any age-appropriate vaccine, for the purposes of this research study we elected to exclude individuals with these allergies\]
* History of Guillain-Barre syndrome (GBS)
* Body temperature greater than 100.3°F (38°C) on date of vaccination or within 2 days prior to vaccination by participant report (study entry may be delayed to meet this requirement)
* Rockwood Frailty Index score of \>0.21
* Known history of any of the following co-morbid conditions:
* Chronic or recent (within past 2 months) infection requiring oral or intravenous antibiotics, antifungals, or antivirals
* Cancer other than basal cell carcinoma requiring active surgical or medical treatment (chemotherapy or radiation therapy)
* Congestive Heart Failure
* Ischemic Heart Disease
* Congenital abnormalities (PI to evaluate)
* Paget's disease
* Renal failure requiring ongoing dialysis
* Chronic obstructive pulmonary disease, emphysema, or asthma
* Severe autoimmune disease requiring biological therapy
* Diabetes mellitus requiring insulin
* Use of medicines during past 6 months known to alter immune response such as high-dose corticosteroids (≥ 10 mg/day of prednisone or equivalent)
* HIV, AIDS or other immunodeficiency disorders
* Recent (≤ 3 months) severe trauma or major surgery (PI to evaluate)
* Current substance and/or alcohol abuse
* Patients currently residing in the Department of Correction
* Inability to comply with the protocol requirements
* Any other condition that, in the opinion of the PI, might interfere with study objectives
