Demonstrate the Lot-to-lot Consistency of 3 Consecutive Batches and to Evaluate the Efficacy and Safety of GC FLU®Pre-filled Syringe Injection and 'GC FLU®Injection' Administration.

This is a Post-Marketing, Multicentre, Open, Randomized Phase 4 Clinical Study. Subjects who gave voluntary written informed consent to participate in the study were screened for eligibility in the study, and those who met the eligibility criteria were randomized in the investigational group.

An investigator assessed the effectiveness (immunogenicity) and safety of the study vaccine in each subject during his/her participation in the study.

Subjects were randomized (Visit 1) into the investigational group according to a randomization table previously generated, and were vaccinated with influenza split vaccine, 'GC FLU®Pre-filled Syringe Injection' and 'GC FLU®Injection'.

12 Assessments for HI titre to each strain of influenza were performed at Visit 1 (pre-vaccination), and at Visit 3 (21 days after vaccination) for the efficacy (immunogenicity) evaluation [Picture 1].For the safety assessment, subject diaries were handed out to subjects, who were instructed to record any adverse event emerging ager the receipt of study vaccine.

Inclusion criteria

• Healthy adults≥ 18 and < 65years of age who can be followed up for 21 days.

Depending on the part of the study that a subject was going to participate, age criteria were further divided as follows:

Lot-to-lot consistency study [PART A]: ≥ 18 to < 65 years of age Annual clinical trial [PART B]: ≥ 18 to < 65 years of age [adults]

• 65 years of age [elderly population]

• Subjects who gave voluntary written consent to participate in the study, and are able to comply with the study requirements.

Exclusion criteria

• Subjects with a known hypersensitivity of allergic reaction to eggs or egg products, to chicken or chichenproducts, to any component of the study vaccine, neomycin or gentanicin.
• Subjects with immune system disorders, including immune deficiency disease.
• Subjects with a history of Guillain-Barre syndrome.
• Subjects with severe chronic disease (e.g., cardiovascular disease except for controlled hypertension, respiratory disease, metabolic disease, renal dysfunction or hemoglobinopathy, etc.) who in the investigator's opinion may have difficulty in participating in the study.
• Subjects with haemophilia or receiving a treatment with an anticoagulant, who are at increased risk of serious bleeding during intramuscular injection.
• Subjects who had acute fever with the body temperature exceeding 38.0 °C within 72 hours before vaccination with the study drug.
• Subjects who had received other vaccinations within 7 days before vaccination with the study drug, or those who had another vaccination scheduled during the study.
• Subjects who had received immunosuppressant or immune modifying drug within 3 months before vaccination with the study drug.