The purpose of this study is to observe the adverse reaction ratio and hemagglutination inhibition (HI) antibody positive rate, Geometric mean titer (GMT) of three brands split influenza virus vaccine in different population.

Observational Objectives:

To describe the safety of evaluated vaccine, given in the two-dose schedule in accordance with the Package Insert, in children aged ≥ 6 months to ≤ 36 months,6th to 12th birthday and ≥ 60th birthday.

To describe the immunogenicity of evaluated vaccine, given in the two-dose schedule in accordance with the Package Insert, in children aged ≥ 6 months to ≤ 36 months, 6th to 12th birthday and ≥ 60rd birthday.

Inclusion Criteria:

• participants were enrolled (toddlers: 6 months to 3 years; school-aged children: 6 to 12 years and older adults: ≥60 years）
• Eligible participants were generally healthy or had stable chronic medical conditions (for older adults only)

Exclusion Criteria:

• History of allergic reaction to any component of the study vaccines or previous influenza vaccine
• History of systemic hypersensitivity to hens' eggs
• History of Guillain Barré syndrome following administration of any influenza vaccine
• Any immunodeficient or immunocompromised conditions
• Receipt of cytotoxic or immunosuppressive drugs within the past 6 months
• Receipt of blood-derived product within the past 3 months
• Receipt of any vaccine within one month prior to study entry with exception of paediatric routine vaccination
• Receipt of non-study 2010-2011 seasonal TIV
• Participation in any other study with a non-approved drug during the study
• Acute febrile disease and other self-limiting illness were the temporary exclusion criteria