Innate and Acquired Immunity to Influenza Infection and Immunization (SLVP029)

Inclusion Criteria:

   1. Otherwise healthy, 6 mo-49 year-old volunteers.

   2. Willing to complete the informed consent process (including assent for minors 7-17
   years of age).

   3. Availability for follow-up for the planned duration of the study.

   4. For parents of children 6 months - 4 years of age: Willing to participate in the study
   annually for up to 5 years (if yes, consider for annual return groups).

   5. Acceptable medical history by review of inclusion/exclusion criteria and vital signs.

   6. Influenza vaccine-naive or only one prior season of flu immunization with IIV (does
   not apply to Groups F and G).

Exclusion Criteria:

   1. Prior off-study vaccination with the current year's seasonal influenza vaccine

   2. Receipt of LAIV in the prior season (does not apply to Groups F and G)

   3. Received flu immunizations in 2 or more prior flu seasons (does not apply to Groups F
   and G)

   4. Allergy to egg or egg products, or to vaccine components, (including gentamicin,
   gelatin, arginine or MSG if given LAIV4)

   5. Life-threatening reactions to previous influenza vaccinations

   6. Asthma in adults. Children aged 2 through 4 years who have asthma or who have had a
   wheezing episode noted in the medical record within the past 12 months, or for whom
   parents report that a health care provider stated that they had wheezing or asthma
   within the last 12 months [If yes, not eligible for LAIV Groups A, B, C, & F].

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

   8. History of immunodeficiency (including HIV infection)

   9. For children or adolescents through 17 years of age,receiving aspirin therapy or
   aspirin-containing products [If yes, not eligible for LAIV Groups A, B, C, and F].

10. 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.

11. Blood pressure >150 systolic or >95 diastolic at first study visit and the day of
   vaccination (for children 12 yrs and older, and adults).

12. Hospitalization in the past year for congestive heart failure or emphysema.

13. Chronic Hepatitis B or C

14. Recent or current use of immunosuppressive medication, including systemic
   glucocorticoids (corticosteroid nasal sprays and topical steroids are permissible in
   all groups; inhaled steroid use is not permissible)

15. Participants in close contact with anyone who has a severely weakened immune system
   and requires a protective environment. Exposure to such persons should be avoided for
   7 days after receipt of LAIV. [If yes, may be ineligible for Groups A,B, C and F].

16. 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).

17. 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

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

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

20. Has taken an influenza antiviral medication within 48 hours prior to study vaccination
   [If yes, not eligible for LAIV Groups A, B, C and F].

21. Receipt of blood or blood products within the past 6 months or planned used during the
   study

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

23. Receipt of inactivated vaccine 14 days prior to study enrollment, or planned
   vaccinations prior to completion of last study visit

24. Receipt of live, attenuated vaccine within 60 days prior to enrollment of planned
   vaccination prior to completion of last study visit

25. Need for allergy immunization (that cannot be postponed) during the study period

26. History of Guillain-Barre syndrome

27. Pregnant woman

28. Breastfeeding [If yes, not eligible for LAIV Group F]

29. Use of investigational agents within 30 days prior to enrollment or planned use during
   the study

30. Donation of the equivalent of a unit of blood within 6 weeks prior to enrollment or
   planned donation prior to completion of the last visit

31. 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.