A Study to Assess the Safety of ASP7374 in Adult Subjects Aged 20 or Older

Inclusion Criteria: * Medically stable, as judged on the basis of history and concurrent diseases * Subject understands procedure of the protocol and is willing to comply with the protocol. Exclusion Criteria: * Scheduled to receive another vaccine during the study. * Received influenza HA vaccine within 180 days prior to screening. * Received or scheduled to receive a live vaccine within 28 days prior to vaccination with the study vaccine, and received or scheduled to receive an inactivated vaccine or a toxoid within 7 days prior to vaccination with the study vaccine. * 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 one of the following medications or treatment prior to vaccination with the study vaccine: * 1\. Within 28 days prior to vaccination with the study vaccine 1. Interferon formulation 2. Drugs which affect the immune system (e.g., immunosuppressants) 3. Systemic corticosteroids and inhaled corticosteroids 4. G-CSF and M-CSF * 2\. Within 84 days prior to vaccination with the study vaccine 1. Human immunoglobulin products 2. Blood products 3. Blood transfusion * 3\. Within 180 days prior to vaccination with the study vaccine 1. High-dose human immunoglobulin products (≥200 mg/kg) * 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) * History of seizures (exclude a pyrexial attack in childhood) * History of Guillain-Barre syndrome or acute disseminated encephalomyelitis (ADEM) * Body temperature of ≥37.5°C on Day 1 (before vaccination) * Moderate to severe acute or febrile illness (≥37.5°C) within 7 days prior to vaccination * Concurrent hepatic disease (exclude fatty liver, hepatic cyst, biliary stone and gallbladder poly, which have laboratory findings only, no clinical symptoms, and not necessary to treat), or AST (GOT) and/or ALT (GPT) of \>100 IU/L at screening on Day 1 * Concurrent renal disease (exclude rental cyst and calculus kidney which have laboratory findings only, no clinical symptoms, and not necessary to treat), or creatinine of \> 1.5 mg/dL at screening * Concurrent respiratory disease, hematologic disease, or developmental disorders * Concurrent or previous heart disease * Concurrent or previous cerebrovascular disorder * Concurrent malignancy or diagnosis or treatment of malignancy within 5 years before screening * Diagnosis of mental disorder including schizophrenia, bipolar disorder, or major depressive disorder or cognitive impairment, or received medications for cognitive impairment * Concurrent disease interfering with the evaluation of local and systemic reactions