The purpose of this study is to evaluate the safety, tolerability, and immunogenicity of GC3106 after single intramuscular administration in Korean healthy adults.

This study is the first in human trial of GC3106 and is designed as an adaptive Phase I/IIa to ensure participants protection. Part A is an open-label and single arm study in 9 healthy volunteers. Data and Safety Monitoring Board (DSMB) will review the solicited/unsolicited adverse events conditionally if any toxicity of Grade 3 or 4 has been reported during 7 days after vaccination from the first 9 healthy volunteers. Part B is a randomized (2:1), double-blind, active controlled study and a total of 75 volunteers will participate in this part. Adverse events assessment will be done according to the 'Toxicity Grading Scale for Healthy Adult and Adolescent Volunteers Enrolled in Preventive Vaccine Clinical Trials'.

Inclusion Criteria:

• Given written informed consent
• Healthy Korean adults (age: between over 19 and under 65)
• Korean adults who agree with 21 days follow up after vaccination and good compliance to study procedures
• Those who are able to comply with the requirements for the study

Exclusion Criteria:

• Inability in written/verbal communication
• Subjects who have participated in other interventional study within 30 days
• Alcohol or drug abuse within 6 months
• Heavy drinkers or subjects who do not agree to stop drinking for 3 days before vaccination and other 3 days after vaccination
• Who got the treatment of psychotropic drugs and narcotic analgesic drugs within 6 months of enrollment
• Hypersensitivity with drug or active ingredient
• Disorders in immune function
• History of Guillain-Barré syndrome
• Disease/medications which are likely to cause any severe bleeding
• Active infection or experience of fever (>38.0 ℃) within 72 hours following vaccination
• Oral temperature >38.0 ℃ at the vaccination day
• Erythema, tattoo, injury at shoulder (vaccination site)
• Influenza vaccination within 6months
• Any vaccination within 30 days
• Concomitant medications/therapy such as immunosuppressants or immune modifying drugs, systemic corticosteroids, immunoglobulins, blood or blood- derived products, or anti-cancer chemotherapy or radiation therapy within3 months
• Pregnant or breast-feeding women
• Clinically significant underlying diseases or medical history at investigator's discretion