This phase II study is intended to determine the immunogenicity and safety of single dose and two doses of OSP:rTTHc cholera conjugate vaccine (CCV) with or without alum adjuvant. The study will guide the future dosing schedule and formulation of CCV (with or without Aluminum phosphate adjuvant) expected to be needed in adults and children in cholera-endemic region.

This is phase II, randomized, controlled, safety and immunogenicity study of one and two doses of the of CCV 25 μg (with and without alum) in cholera-endemic region.

A total of 390 eligible participants will be recruited in the study into 3 age cohorts.

This will be a randomized, placebo-controlled, observer blind study in adults aged 18 to 45 years (cohort A) and children aged 5 to 17 years (cohort B) followed by a randomized, active-controlled, partial open label study in children aged 1 to 4 years (cohort C).

The DSMB must review the safety data of each cohort and approve study continuation before investigational product administration of the next younger cohort is initiated (age descending study scheme).

In cohort A, 50 adult participants aged 18 to 45 years will be randomly divided into 5 arms to receive the assigned investigational product as follows:

Arm A1 (n=10): one dose of CCV 25 μg with alum and one dose of placebo at 6 months interval Arm A2 (n=10): one dose of CCV 25 μg without alum and one dose of placebo at 6 months interval Arm A3 (n=10): two doses of CCV 25 μg with alum at 6 months interval Arm A4 (n=10): two doses of CCV 25 μg without alum at 6 months interval Arm A5 (n=10): two doses of placebo at 6 months interval

In cohort B, 90 children aged 5 to 17 years will be randomly divided into 5 arms to receive the assigned investigational product as follows:

Arm B1 (n=20): one dose of CCV 25 μg with alum and one dose of placebo at 6 months interval Arm B2 (n=20): one dose of CCV 25 μg without alum and one dose of placebo at 6 months interval Arm B3 (n=20): two doses of CCV 25 μg with alum at 6 months interval Arm B4 (n=20): two doses of CCV 25 μg without alum at 6 months interval Arm B5 (n=10): two doses of placebo at 6 months interval

In cohort C, 250 children aged 1 to 4 years will be randomly divided into 10 arms to receive the assigned investigational product as follows:

Arm C1 (n=30): one dose of CCV 25 μg with alum and one dose of placebo at 6 months interval Arm C2 (n=30): one dose of CCV 25 μg without alum and one dose of placebo at 6 months interval Arm C3 (n=30): two doses of CCV 25 μg with alum at 6 months interval Arm C4 (n=30): two doses of CCV 25 μg without alum at 6 months interval Arm C5 (n=20): two doses of placebo at 6 months interval Arm C6 (n=30): two doses of Euvichol®-Plus at 2 weeks interval Arm C7 (n=20): one dose of CCV 25 μg with alum and one dose of Euvichol®-Plus at 6 months interval Arm C8 (n=20): one dose of CCV 25 μg without alum and one dose of Euvichol®-Plus at 6 months interval Arm C9 (n=20): one dose of Euvichol®-Plus and one dose of CCV 25 μg with alum at 6 months interval Arm C10 (n=20): one dose of Euvichol®-Plus and one dose of CCV 25 μg without alum at 6 months interval

Route of vaccination: CCV 25 μg (with or without alum) and placebo are administered by intramuscular (IM) injection. Euvichol®-Plus is administered orally.

Inclusion Criteria:

1. Individuals aged 1 to 45 years at consent
2. Participants/ Participants' legally authorized representative (LAR) willing to provide written informed consent to participate in the study voluntarily
3. Participants who can comply with the study requirements
4. Individuals in good health as determined by the outcome of medical history, physical examination, and the clinical judgment of the investigator

Exclusion Criteria:

1. Known history or allergy to investigational vaccine components or other medications, or any other allergies
2. Individuals with major congenital abnormalities
3. Known history of immune function disorders including immunodeficiency diseases (known HIV infection¥ or other immune function disorders)
4. Use of systemic steroids within past 6 months (>10 mg/day prednisone equivalent for periods exceeding 2 consecutive weeks), or receive chemotherapy, radiation therapy or other immunosuppressive drugs within the past 6 months.
5. Any abnormality or chronic disease which in the opinion of the investigator might be detrimental for the safety of the participant and interfere with the assessment of the study objectives
6. Individuals with behavioral or cognitive impairment or psychiatric disease or neural disorders that, in the opinion of the investigator, could interfere with the participant's ability to participate in the trial
7. Individuals with splenectomy
8. Individuals with known bleeding disorders
9. Receipt of blood, blood-derived products, or immunoglobulin products in the past 3 months
10. Individuals who have received other vaccines from 4 weeks prior to the first dose of test vaccination or planned to receive any vaccine within 4 weeks of the last dose of the investigational product.
11. Individuals with active or known previous Vibrio cholerae infection
12. Individuals with a history of severe diarrhea in the last 6 months requiring care at a medical facility lasting 24 hours or more
13. Individuals with prior receipt of a cholera vaccine in the last 5 years
14. Any female participant who is lactating or pregnant
15. Females of childbearing potential who do not agree to use an effective birth control method for at least 4 weeks before the screening and up to 12 weeks after the study vaccination.
16. Individuals enrolled in another clinical trial within 6 months prior to enrollment, concomitantly enrolled or scheduled to be enrolled in another trial during study period
17. Individuals who are research staff involved with the clinical trial or family/household members of research staff
18. As per Investigator's medical judgement, an individual could also be excluded from the study despite meeting all inclusion/exclusion criteria mentioned above
19. Children below 5 years old with Weight for Height Z score and/or Height for Age Z score of less than -2

The study in cohort A and B will be conducted in an observer blinded manner. Observer-blind means only the designated study site personnel responsible for investigational product preparation will be aware of the investigational product allocation while all other individuals involved in the study (study participants, study investigators, study nurses, and all personnel assessing clinical outcomes) will be blinded to investigational product allocation until final database lock. The study in cohort C will be conducted mostly in an observer blinded manner i.e., the blind will be maintained between arms C1 to C5, between C7 and C8, and between C9 and C10, but will be partially open label (where blinding is not feasible due to the different routes of administration of assigned IP) between the different type of arms i.e. those receiving CCV (C1-5) vs comparator (C6) vs heterologous arms (C7-8 vs C9-10).