Dates: 2016-2018

Challenge agent: Salmonella Typhi

Number of participants: 40

Lead: Professor Andrew Pollard

Oxford Vaccine Group, Centre for Clinical Vaccinology and Tropical Medicine, University of Oxford UK


The TYGER study sort to explore a recently identified virulence factor encoded by S. Typhi and Paratyphi, termed the typhoid toxin. A typhoid toxin-deficient isogenic mutant strain (SB6000) was generated from the wild-type Quailes strain (WT), this was characterised and manufactured to GMP standards. 

Participants were randomised to either the wild-type or toxin-deficient strain. They were then exposed to live S. Typhi bacteria under defined conditions, by asking them to swallow a solution that contains the bacteria. After the challenge the investigators closely monitored participants for a period of at least two weeks and participants were treated with antibiotics if they were diagnosed with typhoid disease or after 14 days if they did not receive a diagnosis. 

The primary endpoint of the study was to compare the proportion of participants developing clinical or microbiologically proven typhoid infection following oral challenge between the toxin-deficient strain and the wild-type strain. Secondary objectives included comparison of disease severity between the two groups.

Challenge studies involving Salmonella Typhi and Paratyphi have been undertaken by over 400 participants in previous Oxford Vaccine Group studies since 2011.

Here is a study CHECKLIST of the tasks, processes and actions required to set the study up.












Public Registration


Explore a comprehensive list of resources, tools and templates that can be used for developing and implementing successful trial studies. You can find more visiting the

Global Health Trials website


 Icons made by Eucalyp, freepik and dDara at