The purpose of this study is to evaluate the immunogenicity and safety of two intramuscular vaccinations with BLB-750 in healthy Japanese adults.

The drug being tested in this study is called BLB-750 that is a vaccine for pandemic influenza infection. This study will evaluate immunogenicity and safety of two intramuscular vaccinations with BLB-750 at 3-week intervals in healthy Japanese adults. The study will enroll 55 participants. BLB-750 will be administered in opened manner:

- Two intramuscular vaccinations of BLB-750 at 3-week intervals, 0.5 mL

This trial will be conducted in Japan. The overall time to participate in this study will be 43 days, starting on the day of first vaccination. Participants will make multiple visits to the clinic, including 21 days after the first vaccination and 21 days after the second vaccination.

Inclusion Criteria:

1. In the opinion of the investigator, 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 man or woman.
4. The participant is aged 20 to 49 years, inclusive, at the time of informed consent.
5. A female participant of childbearing potential who is sexually active with a nonsterilized male partner agrees to use routinely adequate contraception from signing of informed consent throughout the duration of the study.

Exclusion Criteria:

1. The participant has received vaccination with any other investigational products within 4 months prior to vaccination with the study drug.

2. The participant has a history of vaccination with an H5N1 influenza vaccine.

3. The participant has a history of infection with H5N1 virus.

4. The participant is at high risk of contracting H5N1 influenza infection (e.g., poultry workers).

5. The participant is an immediate family member, study site employee, or is in a dependant relationship with a study site employee who is involved in conduct of this study (e.g., spouse, parent, child, sibling) or may consent under duress.

6. The participant has poorly controlled, clinically significant manifestations of neurological, cardiovascular, pulmonary, hepatic, renal, metabolic, gastrointestinal, urologic, endocrine, or other disorders, which may impact their ability to participate as participants or may potentially confound the study results.

7. The participant has a body temperature (oral) ≥37.5°C prior to vaccination with the study drug on Day 1.

8. The participant has any medically diagnosed or suspected immune-deficiency condition.

9. The participant has an immunocompromising 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 vaccination with the study drug.

   Such treatments include, but are not limited to, 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 treatment or other immunosuppressive or cytotoxic drugs.

10. The participant has received antipyretics within 4 hours prior to vaccination with the study drug.

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 anatomic asplenia.

13. The participant has a rash, other dermatologic conditions or tattoos that may interfere with the evaluation of local reaction.

14. The participant has a past or present history of infection with the Hepatitis B Virus (HBV), Hepatitis C Virus (HCV) or Human Immunodeficiency Virus (HIV).

15. The participant has a known hypersensitivity to any component of BLB-750.

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 dependence within 1 year prior to vaccination with the study drug or is unwilling to agree to abstain from excessive alcohol and drugs throughout the study.

18. The participant has received any blood product (e.g., blood transfusion or immunoglobulin) within 90 days prior to vaccination with the study drug.

19. The participant has received any live vaccine within 4 weeks (28 days) prior to vaccination with the study drug or any inactivated vaccine within 2 weeks (14 days) prior to vaccination with the study drug.

20. The participant is a pregnant or lactating woman or wishes to become pregnant before signing informed consent, during, or within 12 weeks after the last vaccination with the study drug or intends to donate ova during such time period.

21. For males: The participant has donated whole blood ≥200 mL within 4 weeks (28 days) or ≥400 mL within 12 weeks (84 days) prior to the first vaccination with the study drug.

    For females: The participant has donated whole blood ≥200 mL within 4 weeks (28 days) or ≥400 mL within 16 weeks (112 days) prior to the first vaccination with the study drug.

22. For males: The participant has donated whole blood ≥800 mL in total within 52 weeks (364 days) prior to the first vaccination with the study drug.

    For females: The participant has donated whole blood ≥400 mL in total within 52 weeks (364 days) prior to the first vaccination with the study drug.

23. The participant has donated blood components within 2 weeks (14 days) prior to the first vaccination with the study drug.

24. In the opinion of the investigator, the participant is unlikely to comply with protocol requirements or is considered ineligible for any other reason.

25. The participant has presence of thrombocytopenia or coagulopathy, or has received anticoagulant therapy within 30 days prior to the first vaccination with the study drug.

Takeda makes patient-level, de-identified data sets and associated documents available for all interventional studies after applicable marketing approvals and commercial availability have been received (or program is completely terminated), an opportunity for the primary publication of the research and final report development has been allowed, and other criteria have been met as set forth in Takeda's Data Sharing Policy (see www.TakedaClinicalTrials.com for details). To obtain access, researchers must submit a legitimate academic research proposal for adjudication by an independent review panel, who will review the scientific merit of the research and the requestor's qualifications and conflict of interest that can result in potential bias. Once approved, qualified researchers who sign a data sharing agreement are provided access to these data in a secure research environment.

Full Analysis Set (FAS): All participants who received at least 1 dose of the study drug for the treatment period.

Up to Day 43

At each visit the investigator had to document any occurrence of adverse events and abnormal laboratory findings. Any event spontaneously reported by the participant or observed by the investigator was recorded, irrespective of the relation to study treatment.