Safety and Immunogenicity of GPO Seasonal Trivalent Inactivated Influenza Vaccine in Healthy Thai Adults

Inclusion Criteria: * Healthy * Age 18-49 years old * Having Thai ID card or equivalent * All hematology, biochemistry and urine analysis are within normal range or of no clinical significance (not higher than 1.5 time of normal value without any clinical finding from history and physical examination) * Able to read and write and sign written informed consent form or assent form. Exclusion Criteria: * Known history of egg allergy * Having had recently influenza infection confirmed as H1N1, H3N2, or Flu B within 3 months preceding enrolment to the trial * Vaccination against influenza in the past 6 months preceding enrolment to the trial * History of bronchial asthma, chronic lung diseases, chronic rhinitis * History of immunodeficiency state * History of immunosuppression \< 6 months prior to immunization * History of anaphylactic or other allergic reactions to influenza vaccine or any vaccine component or excipient (e.g. gentamicin or thimerosal) * Acute infectious with fever \> 38 degree Celsius and noninfectious diseases (within 72 hours) preceding enrollment in the trial * The volunteers who have been taking immunoglobulin products or have had a blood transfusion during past 3 months before the beginning of the experiment * Participation in other research study * Pregnancy or plan to become pregnant for 60 days after enrollment or breast feeding * Current alcohol abuse or drug addiction that might interfere with the ability to comply with trial procedures * Any condition that in the opinion of the investigator would pose a health risk to the subject if enrolled, or could interfere with the evaluation of the vaccine