T-cell And General Immune Response to Seasonal Influenza Vaccine (SLVP018) Year 5, 2013

Inclusion Criteria: 1. Otherwise healthy, twin children age 1-8 years (identical or fraternal twin pairs) 2. Parent willing to sign the informed consent form and child willing to sign assent if indicated. 3. Availability for follow-up for the planned duration of the study at least 28 days after last immunization. 4. Acceptable relevant medical history and vital signs. Exclusion Criteria: 1. Prior off-study vaccination with trivalent inactivated influenza vaccine (IIV3) or live attenuated influenza vaccine (LAIV) in Fall 2013 2. Allergy to egg or egg products, or to vaccine components or thimerosal (if IIV3 multidose vials used) 3. Life-threatening reactions to previous influenza vaccinations 4. Active systemic or serious concurrent illness, including febrile illness on 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. Chronic Hepatitis B or C 8. Recent or current use of immunosuppressive medication, including glucocorticoids (corticosteroid nasal sprays, topical steroids are permissible). History of any cancer. 9. 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. 10. History of blood dyscrasias, or hemoglobinopathies requiring regular medical follow up or hospitalization during the preceding year 11. Use of any anti-coagulation medication such as Coumadin or Lovenox, or anti-platelet agents such as aspirin. 12. Receipt of blood or blood products within the past 6 months or planned receipt of blood products prior to completion of study visits. 13. Medical or psychiatric condition or occupational responsibilities that preclude participant compliance with the protocol 14. Receipt of inactivated vaccine 14 days prior to enrollment, or planned non-study vaccination prior to completion of Visit 03 or 04 (\~Day 28 after the last study vaccination) 15. Receipt of a live, attenuated vaccine within 30 days prior to first vaccination, or planned immunization with a live, attenuated vaccine before completion of study visits (inform study staff of any non-study vaccinations received during the study period). 16. Need for allergy immunization (that cannot be postponed) during the study period. 17. History of Guillain-Barre Syndrome 18. Use of investigational agents within 30 days prior to enrollment or planned use of investigational agents prior to completion of study visits. 19. 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.