Inclusion Criteria:

• Male or female adults ages 18-40 or 65 and older at the time of enrollment.
• Eligible to receive Fluad® (MF59Flu) or Fluzone® (HDFlu) if age 65 or older.
• No history of anaphylactic reaction to gelatin, neomycin, or other vaccine component.
• Not pregnant.
• No immunosuppression or immunodeficiency.
• No acute illness at time of vaccination.
• Determined by medical history and clinical judgment to be eligible for the study, by being generally healthy, with no autoimmune or immunosuppressive conditions and having stable current medical conditions (subjects with preexisting stable disease, defined as disease not requiring significant change in therapy or hospitalization for worsening disease 12 weeks before receipt of study vaccine, will be eligible. A change in dose or therapy within a category (e.g., change from one nonsteroidal anti-inflammatory drug to another) is allowed. A change to a new therapy category (e.g., surgery or addition of a new pharmacological class) is only allowed if it is not caused by worsening disease. A change to a new therapy category caused by worsening disease is considered significant and therefore ineligible for enrollment.
• Patients with diabetes mellitus are eligible for inclusion if they have had a hemoglobin A1c measurement of <8.0 within the past 6 months prior to enrollment. These hemoglobin A1c measurements are recommended at least twice yearly by the American Diabetes Association (ADA), and the target levels here are representative of the goals of the ADA. These hemoglobin A1c levels will ensure that these participants have good glycemic control. (American Diabetes Association. American Diabetes Association Position Statement: Standards of Medical Care in Diabetes— 2015. Diabetes Care 2015;38(Suppl. 1): S1-S94).
• Able to follow study procedures in the opinion of the investigator.
• Expected to be available for the duration of the study.
• Weighs >110 lbs.

Exclusion Criteria: 

• Known or suspected immunodeficiency or receiving treatment with immunosuppressive therapy including cytotoxic agents (e.g., for cancer, HIV, or autoimmune disease).
• Subjects on corticosteroids will be excluded if ≥ 20mg of Prednisone (or equivalent drug) has been (or will be) administered daily for 2 weeks or more. Subjects will be eligible if corticosteroid therapyhas been discontinued for at least 30 days.
• Serious chronic medical conditions including metastatic malignancy, severe chronic obstructive pulmonary disease requiring supplemental oxygen, end-stage renal disease with or without dialysis, clinically unstable cardiac disease, or any other disorder that, in the investigator’s opinion, precludes the subject from participating in the study. Diabetic patients will be excluded if they do not have a hemoglobin A1c measurement within the past 6 months or if they had a hemoglobin A1c measurement of an A1c >8.0.
• Receipt of any blood products, including immunoglobulin, within 6 months of study enrollment.
• Current anticoagulant therapy or a history of bleeding diathesis that would contraindicate intramuscular (IM) injection. (Note: antiplatelet drugs such as aspirin and clopidogrel are permitted).
• Receipt of any vaccines within the past 30 days prior to enrollment.
• Receipt of the current seasonal influenza vaccine other than in this study.
• Acute illness within the last 30 days.
• Blood donation within the last 56 days prior to study enrollment and within 56 days following the last study visit.
• Pregnancy, Nursing or trying to conceive at the time of the study or for 28 days following the baseline visit.
• Any condition (e.g. allergic reaction, Guillain-Barre Syndrome) that precludes their receipt of the influenza vaccine.
• Currently taking antibiotics to treat a serious infection. Preventative use of antibiotics (i.e., oral surgery) is not an exclusion criterion.
• Diagnosis of a cognitive disorder (e.g., Alzheimer’s, Dementia).
• Anemia.
• Any medical condition that would, in the opinion of the investigator, interfere with the evaluation of the study objectives.