To provide Centers for Biologic Evaluation and Research (CBER) with sera collected from healthy children receiving the 2007-2008 formulation of the inactivated, split-virion influenza vaccine Fluzone® for further study.

Inclusion Criteria:

• Participant is aged ≥ 6 months (24 weeks) to < 36 months (3rd birthday).
• Participant is considered to be in good health on the basis of reported medical history and limited physical examination.
• Participant is available for the duration of the study.
• Parent/legal acceptable representative is willing and able to provide informed consent.
• Parent/legal acceptable representative is willing and able to meet protocol requirements.
• Born at full term of pregnancy (≥ 37 weeks) with a birth weight ≥ 2.5 kg (5.5 lbs).

Exclusion Criteria:

• Reported allergy to egg proteins, chicken proteins, or any other constituent of the vaccine.
• An acute illness with or without fever (For infants/toddlers: temperature ≥ 100.4°F rectal; For children: temperature ≥ 99.5°F oral/axillary) in the 72 hours preceding enrollment in the trial (Enrollment may be deferred).
• Clinically significant findings in vital signs or review of systems (Investigator judgment; defer or exclude).
• Participation in any other interventional clinical trial within 30 days prior to enrollment or planned participation in the study.
• Known or suspected impairment of immunologic function, or receipt of immunosuppressive therapy or immunoglobulin since birth.
• Personal or immediate family history of congenital immune deficiency.
• Developmental delay, neurologic disorder, or seizure disorder.
• Chronic medical, congenital, or developmental disorder.
• Known human immunodeficiency virus (HIV)-positive mother.
• Prior personal history of Guillain-Barré syndrome.
• Any condition which, in the opinion of the Investigator, would pose a health risk to the subject or interfere with the evaluation of the vaccine.
• Received any vaccinations within the preceding 14 days (enrollment may be deferred).

Adverse events data were collected from the day of vaccination for 14 days post-vaccination (Influenza Vaccine Primed group) or 42 days post-vaccination (Influenza Vaccine Naïve/Inadequately Primed group)