Immune Non-inferiority and Safety of a Vi-DT Typhoid Conjugate Vaccine

This is a Multicenter, observer-blinded, randomized, Active controlled, Phase 3 study in healthy 6 months to 45 years aged Nepalese at the time of the first vaccine dose.

The study objectives are:

I. Demonstrate non-inferiority of Vi-DT compared to Typbar TCV® as measured by seroconversion rates of anti-Vi IgG ELISA antibody titers, 4 weeks after single dose (pooled immunogenicity of three lots of Vi-DT)

II. Demonstrate the equivalence of immunogenicity as measured by anti-Vi IgG GMT of three lots of Vi-DT vaccine 4 weeks after single dose.

Subjects will be stratified according to age. The study procedure is as follows:

Visit 1 (day-1 to -7): Screen participants by medical/medications history, physical examination, Vital signs, Urine pregnancy test (UPT)

Visit 2 (day 0): Enroll, randomize and administer vaccine to eligible participants and assess participant safety by physical examination and Vital signs, Collect blood for immunogenicity assessments.

Visit 3 (day 7): Check solicited adverse reaction 7 days post vaccination and Assess participant safety by physical examination and Vital signs

Visit 4 (day 28): Assess participant safety by physical examination and Vital signs, Collect blood for immunogenicity assessments

Visit 5 (day 84): Assess participant safety by physical examination and Vital signs

Visit 6 (day 168): Assess participant safety by physical examination and Vital signs, Collect blood for immunogenicity assessments, and fill in study completion form in the absence of any safety concern.

This study is observer-blind: vaccine administrator and vaccine safety evaluator will be two distinct persons to avoid bias of safety assessment. Trial staff other than the vaccine administrator.

For retention: After vaccination, field health worker/designee will contact participant every day till Day 7 by physical visit or by phone call. Follow-up reminder calls will be done very frequently as per discretion of study staff until 24 weeks for all participant to assess participant safety.

Eligibility Criteria:
Inclusion Criteria:

1. Healthy participants 6 months to 45 years of age at enrollment
2. Participants/Parents/LAR who have voluntarily given informed consent/assent
3. Participants/Parents/LAR willing to follow the study procedures of the study and available for the entire duration of the study

Exclusion Criteria:

1. Child with a congenital abnormality
2. Subject concomitantly enrolled or scheduled to be enrolled in another trial
3. Known history of immune function disorders including immunodeficiency diseases (Known HIV infection or other immune function disorders)
4. Chronic use of systemic steroids (\>2 mg/kg/day or \>20 mg/day prednisone equivalent for periods exceeding 10 days), cytotoxic or other immunosuppressive drugs
5. Receipt of blood or blood-derived products in the past 3 months
6. Subject with a previously ascertained or suspected disease caused by S. Typhi
7. Subject who have had household contact with/and or intimate exposure to an individual with laboratory-confirmed S. Typhi
8. Individual who has previously received a typhoid vaccine
9. Subject who has received or is expected to receive other vaccines from 1 month prior to IP vaccination to Visit 4 (approx.1 month post IP) except PVC booster as per EPI schedule
10. Known history or allergy to vaccines or other medications
11. History of uncontrolled coagulopathy or blood disorders
12. Any abnormality or chronic disease which in the opinion of the investigator might be detrimental for the safety of the subject and interfere with the assessment of the study objectives
13. Any female participant who is lactating, pregnant\* or planning for pregnancy during the course of study period
14. Participants/Parents/LAR planning to move from the study area before the end of study period
15. As per Investigator's medical judgement individuals could be excluded from the study inspite of meeting all inclusion/exclusion criteria mentioned above

    Temporary Contraindication
16. Acute illness, in particular infectious disease or fever (axillary temperature ≥37.5°C), within three days prior to enrolment and vaccination.

    * Urine pregnancy test (UPT) will be performed in all married females prior to injection