Phase 1 dose-finding test of a bivalent Klebsiella pneumoniae vaccine in healthy adults

Inclusion Criteria:

* Male or non-pregnant female, aged 18 to 50 years old (inclusive) for Cohorts 1 and 2 at the Screening visit.
* Body mass index (BMI) of 18.0 to 30.0 kg/m2 (inclusive) at the Screening visit.
* Physically and mentally capable of participating in the study and willing to adhere to study procedures.
* Able to provide signed informed consent.
* In generally good health by medical history, physical examination, vital signs, and clinical laboratory findings at the Screening visit based on the investigator's judgment.
* Negative serology test for human immunodeficiency virus (HIV) antibody, hepatitis B surface antigen, and hepatitis C antibody at the Screening visit.
* Female subject with childbearing potential must have a negative result of pregnancy test at the Screening visit.
* Female subject with childbearing potential must be willing to implement adequate, highly effective contraceptive measure during the study period.
* Male subject who agrees to use an adequate method of contraception during the study period.

Exclusion Criteria:

* Any medical or psychiatric condition that, in the opinion of the investigator, may interfere with optimal participation in the study or place the subject at increased risk of AEs.
* Suspected or known hypersensitivity (including allergy) to any of the vaccine components.
* History of hypersensitivity or allergy to any vaccine, especially pneumococcal vaccine.
* Current or previous, confirmed, or suspected disease caused by Klebsiella pneumoniae.
* Medical conditions as a contraindication to the intramuscular vaccination and blood draws, e.g., coagulation disorder.
* Any abnormality or permanent body art (e.g., tattoo) that would interfere with the observation of local reactions at the injection site (deltoid region).
* Acute or chronic, clinically significant cardiovascular, pulmonary, hepatic or renal diseases and/or insufficiency as determined by physical examination or laboratory tests.
* Known or suspected impairment of immunological function, e.g., asplenia/splenectomy or history of autoimmune/immune-mediated diseases or lymphoproliferative disorders.
* Any screening laboratory abnormalities that are Grade 2 or above or deemed clinically significant in the opinion of the investigator.
* Subjects with an electrocardiogram (ECG) at the Screening visit that demonstrates clinically relevant abnormalities which may affect subject safety or study results in the opinion of the investigator.
* Positive test for SARS-CoV-2 virus at the Screening visit.
* Use of any antibiotic therapy within 1 week prior to the first study vaccination.
* History of any chronic or progressive disease that, according to judgment of the investigator, could interfere with the study outcomes or pose a threat to the subject's health.
* History of cancer (except localized skin cancer without metastases) within 5 years prior to the Screening visit.
* History or presence of heavy smoking (defined as \> 10 cigarettes per day; approximately half pack per day) as documented in medical chart or by verbal confirmation at the Screening visit.
* Documented history of substance or alcohol abuse in the medical chart or by verbal confirmation within 6 months prior to the Screening visit.
* Received any vaccination (live, inactivated, or bacterial) within 1 month prior to the Screening visit and plans to receive vaccination within 4 weeks after the last study vaccination during the study period. Exception can be made with marketed vaccines against seasonal influenza or COVID-19 outside the 28-day window of the study vaccination.
* Received major surgery or radiation therapy within 3 months prior to the Screening visit.
* Onset of influenza-like illness as defined by: fever (temperature ≥ 38℃), dry cough, headache, fatigue, respiratory sputum production, dysgeusia, anosmia, shortness of breath, muscle and joint pain, or sore throat within 1 week prior to the Screening visit.
* Female subject who is pregnant or lactating at the Screening visit or plans to be pregnant during the study period or lactate from the time of the first vaccination through 60 days after the last vaccination.
* Received any investigational drug or device or have participated in a clinical study within 3 months prior to the Screening visit.
* Any confirmed or suspected abnormal immune function, immunosuppression, or immunodeficiency or received any immunosuppressants (including systemic corticosteroids) or immunomodulators within 3 months prior to the Screening visit.
* Had blood donation within 2 weeks prior to the Screening visit.
* Received any blood products or immunoglobulin within 3 months prior to the Screening visit.