Typhoid fever Infections and Infestations
Conditions
Interventions
This is a randomised, observer and participant-blinded two-arm non-inferiority trial designed to compare the immunogenicity of a booster dose of either Vi-TT (homologous) or Vi-CRM197 (heterologous) v
OxTREC 15-17). Participants vaccinated with vi-TT in the TyVAC study who were aged 9 months to 2.5 years of age at the time of vaccination will be eligible for inclusion in the trial.
Participants wi
Sponsors
University of Oxford
Eligibility
Sex/Gender
All
Age
5 Years to 10 Years
Inclusion criteria
Inclusion criteria: The participant must satisfy all the following criteria to be eligible for enrolment: 1. Parent/legal guardian is willing and competent to provide informed consent. If the participant is 7 years of age or older, assent will also be sought 2. Between 9 months and 2.5 years of age at time of initial vaccination with Vi-TT 3. In good health on the day of vaccination according to the attending doctor 4. Parent/legal guardian confirms that their child will be willing and able to comply with study requirements including follow-up contact, according to the schedule 5. Live within the study catchment area at the time of booster vaccination
Exclusion criteria
Exclusion criteria: The participant will not be enrolled if any of the following criteria apply: 1. They have a known allergy to any of the vaccine components 2. Any medical or social reasons that will prevent the participant from conforming to the study requirements as judged by a medical professional 3. Any congenital or acquired immunodeficiency that could impact vaccine responses 4. They are planning to move away from the catchment area within the next 6 months
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| Current primary outcome measure as of 09/06/2025: The immunogenicity following a homologous or heterologous booster vaccination in children who received a single dose of Vi-TT at <2.5 years old is measured using anti-Vi IgG levels in a blood sample taken at 28 days post booster vaccination. _____ Previous primary outcome measure: The immunogenicity following a homologous or heterologous booster vaccination in children who received a single dose of Vi-TT at <2.5 years old is measured using anti-Vi IgG and anti-Vi IgA levels in a blood sample taken at 28 days post booster vaccination. | — |
Secondary
| Measure | Time frame |
|---|---|
| 1. Vaccine safety, measured as the proportion of participants developing all adverse events within the first 7 days post-vaccination, and serious adverse events within 6 months of vaccination as determined through self-reporting at follow-up contacts at 7 days, 28 days and 6 months post booster vaccination 2. The kinetics of immunogenicity following heterologous and homologous boosters in children who received a single dose of Vi-TT at <2.5 years old will be measured using anti-Vi IgG and anti-Vi IgA levels in blood samples taken at Day 0 (pre booster), Day 28, 6 months and 18 months post booster vaccination. 3. The incidence of typhoid and paratyphoid disease in the boosted participants measured through blood culture confirmed cases of typhoid or paratyphoid fever from passive surveillance in participants throughout the study period | — |
Countries
Nepal
Contacts
Public ContactAndrew;Shrijana Pollard;Shrestha
;
Outcome results
None listed