T-cell And General Immune Response to Seasonal Influenza Vaccine (SLVP018) Year 4, 2012

Inclusion Criteria:

   1. Otherwise healthy, ambulatory adults, ages 18-30 years (identical or fraternal twin
   pairs), 40-64 years (identical or fraternal twin pairs) or 65-100 years (identical
   twin pairs).

   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.

Exclusion Criteria:

   1. Prior off-study vaccination with trivalent inactivated influenza vaccine (TIV) or live
   attenuated influenza vaccine (LAIV) in Fall 2012

   2. Allergy to egg or egg products, or to vaccine components (including gentamicin,
   gelatin, arginine or MSG (LAIV for Group B only), and thimerosal (if TIV multidose
   vials used)

   3. Life-threatening reactions to previous influenza vaccinations

   4. Active systemic or serious concurrent illness, including febrile illness the day of
   vaccination

   5. History of immunodeficiency (including HIV infection)

   6. 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 or any other chronic disorder which, in the opinion of the
   investigator, might jeopardize volunteer safety or compliance with the protocol.

   7. Blood pressure >150 systolic or > 95 diastolic at Visit 1

   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, topical steroids and inhaled steroids are permissible).
   Use of oral steroids (<20mg prednisone-equivalent/day) may be acceptable after review
   by the investigator.

11. 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).

12. 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.

13. History of blood dyscrasias, renal disease, or hemoglobinopathies requiring regular
   medical follow up or hospitalization during the preceding year

14. Use of any anti-coagulation medication such as Coumadin or Lovenox, or anti-platelet
   agents such as aspirin (except aspirin up to 325 mg.day), Plavix, or Aggrenox must be
   reviewed by investigator to determine if this would affect the volunteer's safety.

15. Receipt of blood or blood products within the past 6 months or planned receipt of
   blood products prior to completion of study visits.

16. Medical or psychiatric condition or occupational responsibilities that preclude
   participant compliance with the protocol

17. Receipt of inactivated vaccine 14 days prior to study vaccination, or planned
   non-study vaccination prior to completion of Visit 03 (~Day 28 after the study
   vaccination)

18. Receipt of live, attenuated vaccine within 60 days of vaccination, or planned
   non-study vaccination prior to completion of Visit 03 (~Day 28 after the study
   vaccination)

19. Need for allergy immunization (that cannot be postponed) during the study period V01
   to V03 (~Day 28)

20. History of Guillain-Barre Syndrome

21. Pregnant or lactating woman

22. Use of investigational agents within 30 days prior to enrollment or planned use of
   investigational agents prior to completion of study visits.

23. Donation of the equivalent of a unit of blood within 6 weeks prior to enrollment or
   planned blood donation prior to completion of Visit 03 ( ~28 Day after study
   vaccination)

24. A current member of the clinical study team.

25. 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.

26. Asthma or history of wheezing (for Group B volunteers only)

27. Participants in close contact with anyone who has a severely weakened immune system
   should not receive LAIV (for Group B volunteers only)