Typhoid conjugate vaccine booster study in Nepal

ISRCTN	ISRCTN91882592
DOI	https://doi.org/10.1186/ISRCTN91882592
Sponsor	University of Oxford
Funder	Wellcome Trust

Submission date: 13/05/2026
Registration date: 25/06/2026
Last edited: 25/06/2026

Recruitment status: Recruiting
Overall study status: Ongoing
Condition category: Infections and Infestations

Prospectively registered

Protocol

Statistical analysis plan

Results

Individual participant data

Record updated in last year

Plain English summary of protocol

Not provided at time of registration

Contact information

Prof Andrew Pollard
Principal investigator, Scientific, Public

Oxford Vaccine Group
Department of Paediatrics
University of Oxford
University of Oxford Centre for Clinical Vaccinology & Tropical Medicine (CCVTM)
Churchill Hospital
Oxford
OX3 7LE
United Kingdom

Phone	+44 (0)1865 611400
Email	info@ovg.ox.ac.uk

Prof Shrijana Shreshta
Scientific, Principal investigator

Patan Academy of Health Sciences (PAHS)
Kathmandu
26500
Nepal

Phone	+977 (0)1 5445 112
Email	pahs@pahs.edu.np

Study information

Primary study design	Interventional
Allocation	Randomized controlled trial
Masking	Blinded (masking used)
Control	Active
Assignment	Parallel
Purpose	Prevention
Scientific title	Comparative study on safety and immunogenicity of homologous versus heterologous prime-boost Typhoid Conjugate Vaccine (TCV) schedules in Nepalese children
Study objectives
Ethics approval(s)	Not yet submitted
Health condition(s) or problem(s) studied	Typhoid fever; evaluation of booster typhoid conjugate vaccination schedules and immunogenicity in children previously vaccinated with typhoid conjugate vaccine.
Intervention	This study is a randomised, observer- and participant-blind, parallel-group comparative study in children in Kathmandu Valley, Nepal, who were previously vaccinated with Vi-CRM197 typhoid conjugate vaccine. Participants will be randomised 1:1 by computer to receive either a homologous booster (Vi-CRM197) or a heterologous booster (Vi-TT/Typbar-TCV). Follow-up will continue for approximately 18 months and will include immunogenicity blood sampling, safety monitoring, scheduled follow-up visits and passive surveillance for enteric fever outcomes.
Intervention type	Biological/Vaccine
Phase	Phase III/IV
Drug / device / biological / vaccine name(s)	Vi polysaccharide-tetanus toxoid conjugate vaccine (Vi-TCV) [Tybar-TCV], Vi polysaccharide conjugated to CRM197 (Vi-CRM197) [TYPHIBEV®]
Primary outcome measure(s)	Anti-Vi IgG and IgA antibody responses measured using laboratory immunoassays (ELISA) to assess anti-Vi IgG and anti-Vi IgA antibody concentrations in plasma samples at Day 28 post-booster vaccination
Key secondary outcome measure(s)	Anti-Vi IgG and IgA antibody responses measured using laboratory immunoassays (ELISA) to assess anti-Vi IgG and anti-Vi IgA antibody concentrations in plasma samples at 6 and 18 months Vaccine safety measured using data collected on the proportion of participants developing all adverse events within the first 7 days post-vaccination, and serious adverse events at 7 days, 28 days and 6 months post booster vaccination The incidence of typhoid and paratyphoid disease in the boosted participants measured using blood culture confirmed cases of typhoid or paratyphoid fever from passive surveillance in participants at throughout the study period
Completion date	30/06/2028

Eligibility

Participant type(s)
Age group	Child
Lower age limit	4 Years
Upper age limit	6.5 Years
Sex	All
Target sample size at registration	240
Key inclusion criteria	Children living in Kathmandu Valley, Nepal, who: 1. Previously received a single dose of Vi-CRM197 typhoid conjugate vaccine at 15–20 months of age through the national immunisation programme or catch-up campaign 2. Are at least 4 years post-primary vaccination at enrolment (typically aged 5–6.5 years) 3. Have verifiable documentation of prior vaccination 4. Are in good health on the day of vaccination according to the attending doctor 5. Have a parent/legal guardian willing and able to provide informed consent and support study follow-up 6. Live within the study catchment area
Key exclusion criteria	1. Unable to provide verifiable documentation of prior Vi-CRM197 vaccination 2. Known allergy to any vaccine component 3. Any medical or social condition that may prevent compliance with study procedures or follow-up 4. Known congenital or acquired immunodeficiency that could affect vaccine responses 5. Planning to move away from the study catchment area during follow-up 6. Temporary exclusion at the time of vaccination due to reported fever within the previous 24 hours or receipt of another vaccination within the previous 48 hours
Date of first enrolment	01/07/2026
Date of final enrolment	31/01/2027

Locations

Countries of recruitment

Nepal

Study participating centres

Results and Publications

Individual participant data (IPD) Intention to share	Yes
IPD sharing plan	The datasets generated during and/or analysed during the current study will be available upon request from Prof. Andrew Pollard (info@ovg.ox.ac.uk).

Editorial Notes

20/05/2026: Study’s existence confirmed by the Research Governance, Ethics & Assurance, University of Oxford, UK.