This trial is to investigate the clinically recommended dosage for ASP7373 based on the comparison of the immunogenicity and safety among the three doses of ASP7373 in healthy adults.

Inclusion Criteria:

• Body weight: Female: ≥40.0 kg, <70.0 kg, Male: ≥50.0 kg, <80.0 kg
• BMI: ≥17.6, <26.4
• Healthy, as judged by the investigator or sub-investigator based on the results of physical examinations (subjective symptoms and objective findings) and all tests obtained

Exclusion Criteria:

• Scheduled to receive another vaccine during study period
• History of H5 influenza infection or received H5 influenza vaccine
• Past history of anaphylactic shock or an allergic reaction such as generalized eruption due to food or drug (including vaccines) allergies, fever ≥ 39.0°C within 2 days after the previous vaccination (influenza vaccine and others)
• Diagnosis of immune deficit in the past, has a family member (within the third degree of kinship) with a diagnosis of congenital immunodeficiency syndrome
• Received or scheduled to receive a live vaccine within 28 days prior to vaccination of the study vaccine, and received or scheduled to receive an inactivated vaccine or a toxoid within 7 days prior to vaccination of the study vaccine
• History of seizures
• Female subjects who are breastfeeding, pregnant, possibly pregnant, and planning to become pregnant during the study period