Phase 2 Study of TAK-850 in Comparison With Influenza Hemagglutinin (HA) Vaccine in Healthy Adult Participants

Inclusion Criteria:

1. In the opinion of the investigator or subinvestigator, the participant is capable of understanding and complying with protocol requirements.
2. The participant signs and dates a written, informed consent form prior to the initiation of any study procedures.
3. The participant is a healthy Japanese adult male or female.
4. The participant is aged 20 to 49 years, inclusive, at the time of informed consent.
5. The participant has a body mass index (BMI) between 18.5 and 25.0 kg/m^2, inclusive, at the time of the eligibility evaluation.
6. A female participant of childbearing potential who is sexually active with a nonsterilized male partner agreed to routinely use adequate contraception from signing of the informed consent throughout the duration of the study.

Exclusion Criteria:

1. The participant has received any investigational compound within 4 months prior to injection of study vaccine.
2. The participant has been vaccinated with seasonal influenza vaccine within 6 months prior to injection of study vaccine.
3. The participant has a history of influenza infection within 6 months prior to injection of study vaccine.
4. The participant has been vaccinated with TAK-850 before.
5. The participant is a study site employee, an immediate family member of such an employee, or in a dependent relationship with a study site employee who is involved in the conduct of this study (e.g., spouse, parent, child, sibling), or may consent under duress.
6. The participant has uncontrolled, clinically significant manifestations of neurological, cardiovascular, pulmonary, hepatic, renal, metabolic, gastrointestinal, urologic, endocrine, or other disorders, which may impact the ability of the participant to participate or potentially confound the study results.
7. The participant has an oral temperature >= 37.5 °C prior to injection of study vaccine on Day 1.
8. The participant has any medically diagnosed or suspected immune deficient condition.
9. The participant has an immune compromising condition or disease, or is currently undergoing a form of treatment or was undergoing a form of treatment that can be expected to influence immune response within 30 days prior to injection of study vaccine. Such treatments include systemic or high dose inhaled corticosteroids (> 800 µg/day of beclomethasone dipropionate or equivalent; the use of inhaled and nasal steroids that do not exceed this level will be permitted), radiation therapy, and other immunosuppressive and cytotoxic drugs.
10. The participant has received antipyretics within 4 hours prior to the injection of study vaccine.
11. The participant has a history of Guillain-Barré Syndrome, demyelinating disorders (including acute disseminated encephalomyelitis [ADEM] and multiple sclerosis), or convulsions.
12. The participant has a functional or surgical asplenia.
13. The participant has a rash, other dermatologic conditions, or tattoos which may interfere with the evaluation of injection site reaction.
14. The participant has a history of, or is infected with the Hepatitis B Virus (HBsAgs), Hepatitis C Virus (HCV), or Human Immunodeficiency Virus (HIV).
15. The participant has known hypersensitivity to any component of TAK-850 or Influenza HA Vaccine.
16. The participant has a history of severe allergic reactions or anaphylaxis.
17. The participant has a history of drug abuse (defined as any illicit drug use) or a history of alcohol abuse within 1 year prior to injection of study vaccine or is unwilling to agree to abstain from excessive alcohol and drugs throughout the study.
18. The participant has received any blood products (blood transfusion or immunoglobulin) within 90 days prior to injection of study vaccine.
19. The participant has received a live vaccine within 4 weeks (28 days) or an inactivated vaccine within 2 weeks (14 days) prior to injection of study vaccine.
20. If female, the participant is pregnant or lactating or intending to become pregnant before signing of informed consent, during treatment, or within 12 weeks after injection of study vaccine; or intending to donate ova during this time period.
21. The participant has donated whole blood >= 200 mL within 4 weeks (28 days), >= 400 mL within 12 weeks (84 days), >= 800 mL within 52 weeks (364 days) or blood components within 2 weeks (14 days) prior to injection of study vaccine.
22. The participant has abnormal laboratory values that suggest a clinically significant underlying disease at the assessment prior to the injection of study vaccine, or the participant has the following laboratory abnormalities: alanine aminotransferase (ALT) and/or aspartate aminotransferase (AST) more than 3 times the respective upper limits of normal.
23. In the opinion of the investigator or subinvestigator, the participant is unlikely to comply with protocol requirements or is considered ineligible for any other reasons.