Each potential subject will be screened before the start of the study to determine their eligibility for participation. Just prior to vaccination, a 10 mL venous blood sample will be taken from each eligible subject, for baseline titration of circulating anti-HA antibodies. Immediately thereafter, each subject received one dose of vaccine (0.5 mL) by intramuscular injection into the upper arm. Subjects will be asked to stay at the site for 30 minutes post-vaccination to observe for immediate reaction. Subjects will be monitored for adverse events during the study. At three weeks (±3 days) after the vaccination, subjects will be asked to return to the site for final collection of blood samples.

Inclusion Criteria:

• Males and non-pregnant females and aged ³ 18 years;
• Willing and able to adhere to visit schedules and all study requirements;
• Subjects read and signed the study-specific informed consent.

Exclusion Criteria:

• Subject or his/her family is employed by the participated hospital;
• 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;
• Patients with influenza-like illness as defined by the presence of fever (temperature ≥38ºC) 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 within 1 month of study vaccination;
• Receipt of any inactivated vaccine within 2 weeks prior to study vaccination or expected receipt within 1 month of study vaccination;
• 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.