This is an open study of the use of AdimFlu-S (2010-2011 season) vaccine in young subjects aged between 6 months old to 18 years old. All participants will be divided into three age cohorts. First, participants aged 6 through < 36 months will receive 2 doses of 0.25 mL vaccine separated by 4 weeks. Second, participants aged 3 through < 9 years will receive 2 doses of 0.5 mL vaccine separated by 4 weeks. Third, participants aged 9 through < 18 years will receive one dose of 0.5 mL vaccine. Safety outcomes included immediate reactions at the time of vaccination, solicited local and systemic reactions within 7 days after each vaccination, unsolicited adverse events, and serious adverse events. Sera prepared from blood samples will be collected from each subject immediately prior to, and 4 weeks after each vaccination. Anti-hemaglutinin (HA) antibody titers will be determined using the WHO haemaglutination inhibition reference technique. The analysis will be observer-blinded. All participants will be followed, either by clinical visit or by telephone contact, for 6 months after the first vaccination for safety reasons.

Inclusion Criteria:

• Boys or girls and aged 6 months old to 18 years old on the day of first vaccination;
• Subject and/or parents(s)/legal guardian(s) must be willing to comply with planned study procedures and be available for all study visits;
• Subject must be in good physical health on the basis of medical history, physical examination;
• Subject and/or parents(s)/legal guardian(s) must read and signed the study-specific informed consent prior to initiation of any study procedure.

Exclusion Criteria:

• Subjects received influenza vaccine (Trivalent and/or A(H1N1)) within the previous 6 months;
• History of hypersensitivity to eggs or egg protein or similar pharmacological effects to study medication;
• Personal or family history of Guillain-Barré Syndrome;
• An acute febrile illness within 1 week prior to vaccination;
• Current upper respiratory illness (URI), including the common cold or nasal congestion within 72 hours;
• Subjects with influenza-like illness as defined by the presence of fever (temperature ³38ºC) and at least two of the following four symptoms: headache, muscle/joint aches and pains (e.g. myalgia/arthralgia), sore throat and cough;
• Female subjects who are pregnant, lactating or likely to become pregnant during the study; Women of childbearing potential disagree to use an acceptable method of contraception (e.g., hormonal contraceptives, IUD, barrier device or abstinence) throughout the study;
• Treatment with an investigational drug or device, or participation in a clinical study, within 3 months before consent;
• Immunodeficiency, immunosuppressive or household contact with immunosuppression;
• History of wheezing or bronchodilator use within 3 months prior to study vaccine;
• Receipt of live virus vaccine within 1 month prior to study vaccine or expected receipt vaccination before the last blood sampling for immunogenicity evaluation;
• Receipt of any inactivated vaccine within 2 weeks prior to study vaccination or expected receipt vaccination before the last blood sampling for immunogenicity evaluation;
• Receipt of any blood products, including immunoglobulin in the prior 3 months;
• Underlying condition in the investigators' opinion may interfere with evaluation of the vaccine;
• Significant chronic illness for which inactivated influenza vaccine is recommended or commonly used.