This study will compare influenza vaccine responses in monozygotic and dizygotic twins.

The investigators plan to study the response to different influenza vaccines much more broadly and deeply across different age groups and with different vaccine modalities and to probe the influence of genetics on these responses using monozygotic and dizygotic twins.

Inclusion Criteria:

1. Otherwise healthy, ambulatory children or adults, ages 8-17 years (identical twin pairs), 18-30 years (identical or fraternal twin pairs), 40-49 years (identical or fraternal twin pairs) or 70-100 years (twin or non-twin adults).
2. Willing to complete the informed consent process.
3. Availability for follow-up for the planned duration of the study at least 28 days after immunization.
4. Acceptable medical history and vital signs.
5. Negative urine pregnancy test for women of childbearing potential
6. If the subject is female and of childbearing potential, she must use an acceptable method of contraception and not become pregnant for the duration of the study. (Acceptable contraception includes implants, injectables, combined oral contraceptives, effective intrauterine devices (IUDs), sexual abstinence, or a vasectomized partner).

Exclusion Criteria:

1. Prior vaccination with TIV or LAIV in Fall 2009
2. Allergy to egg or egg products, or to vaccine components, including gentamicin, gelatin, arginine or MSG (for LAIV only), or thimerosal (TIV multidose vials only).
3. Life-threatening reactions to previous influenza vaccinations
4. Asthma (LAIV groups only)
5. Active systemic or serious concurrent illness, including febrile illness on the day of vaccination
6. History of immune deficiency
7. Known or suspected impairment of immunologic function, including, but not limited to, clinically significant liver disease, diabetes mellitus treated with insulin, moderate to severe renal disease, blood pressure >150/95 at screening, or any other chronic disorder which, in the opinion of the investigator, might jeopardize volunteer safety or compliance with the protocol.
8. Hospitalization in the past year for congestive heart failure or emphysema.
9. Chronic Hepatitis B or C
10. Recent or current use of immunosuppressive medication, including glucocorticoids (corticosteroid nasal sprays are permissible).
11. Subjects in close contact with anyone who has a severely weakened immune system should not receive LAIV.
12. Malignancy, other than squamous cell or basal cell skin cancer (includes solid tumors such as breast cancer or prostate cancer with recurrence in the past year, and any hematologic cancer such as leukemia).
13. Autoimmune disease (including rheumatoid arthritis treated with immunosuppressive medication such as Plaquenil, methotrexate, prednisone, Enbrel) which, in the opinion of the investigator, might jeopardize volunteer safety or compliance with the protocol.
14. History of blood dyscrasias, renal disease, or hemoglobinopathies requiring regular medical follow up or hospitalization during the preceding year
15. Use of any anti-coagulation medication such as Coumadin or Lovenox, or anti-platelet agents such as aspirin, Plavix, Aggrenox may be acceptable after review by investigator.
16. Receipt of blood or blood products within the past 6 months
17. Medical or psychiatric condition or occupational responsibilities that preclude subject compliance with the protocol
18. Inactivated vaccine 14 days prior to vaccination
19. Live, attenuated vaccine within 60 days of vaccination
20. History of Guillain-Barre Syndrome
21. Pregnant or lactating woman
22. Use of investigational agents within 30 days prior to enrollment
23. Donation of the equivalent of a unit of blood within 6 weeks prior to enrollment
24. Any condition which, in the opinion of the investigator, might interfere with volunteer safety, study objectives or the ability of the participant to understand or comply with the study protocol.

Participants between the ages of 8 - 100 years old.

Day 0 to Day 28 of study participation

Clinical Assessment performed at each visit