UHBW launches rare human challenge study testing new vaccine against typhoid fever

Volunteers are needed to take part in a new clinical study testing a new vaccine preventing typhoid and paratyphoid fever.

People aged 18 to 55 years old and in good health are invited to take part in the new BiVISTA clinical study, run by the Vaccine and Testing Research Team at University Hospitals Bristol and Weston NHS Foundation Trust (UHBW), in collaboration with the University of Oxford’s Vaccine Group.

Every year, it is estimated that there are 13 million cases of typhoid and paratyphoid A fever combined, resulting in 133 thousand deaths, mainly affecting school-aged children in Asia and Africa.

The trial is aimed at generating a protective immune response to enteric fever, which is caused by typhoid and paratyphoid. It will involve controlled exposure of participants to live paratyphoid bacteria to evaluate the vaccine’s effectiveness in a safe and controlled environment (known as a human challenge study). Participants will receive either the experimental vaccine or a control vaccine and, one month later, will be exposed to the bacteria under carefully monitored conditions.

Funded by the Serum Institute of India and located locally at the NIHR Bristol Clinical Research Facility (CRF), the total study participation time is seven months. Participants will be reimbursed for their time and travel, receiving up to £4,410 if they remain in the study for the entire period and attend all appointments.

Dr Rajeka Lazarus, UHBW Honorary Consultant Microbiology and Infectious Diseases, Principal Investigator and Consultant Senior Lecturer Consultant in Infectious Diseases and Vaccinology at University of Bristol, UHBW, said: “There are existing safe and effective vaccines against typhoid fever. However, there are no licensed vaccines against Salmonella Paratyphi A – which causes paratyphoid fever and is responsible for around 3 in every 10 cases of enteric fever. There are vaccines in development, but designing a vaccine is difficult as it is not yet understood exactly what immune responses may protect individuals from disease. 

“Human challenge studies – which are relatively rare at UHBW - play a vital role in supporting the development of vaccines and treatments for serious diseases. We hope by investigating this new vaccine we can assist in progressing medical research and saving lives.”

Professor Sir Andrew Pollard, Director of the Oxford Vaccine group, and Chief Investigator of the BiVISTA study, said: "This is a landmark moment in the fight against enteric fever. Not only would this be the first licensed vaccine specifically for paratyphoid A, but this could also be the first combined vaccine to be licensed to protect against both paratyphoid and typhoid.

“If successful, this vaccine could significantly reduce the global burden of enteric fever, a disease that continues to affect millions in low-income countries."

In the last year, UHBW has facilitated 589 research studies, with 5,290 participants giving up their time to support clinical research.

Matt took part in a research study at UHBW between 2023 and 2025 at the NIHR Bristol CRF, which evaluated an investigational vaccine to see if it can prevent mpox (previously known as monkeypox) and smallpox.

Matt said: “When I signed up for the research study, I was relatively apprehensive as I'd never done anything like it before so was unsure what to expect. Having now completed it, I'll most definitely be signing up again if it's at UHBW. The team could not have been more welcoming, patient and considerate throughout the whole study.

“Not only were they extremely professional but they were very generous with their time, answering all my questions and ensuring I knew what symptoms to look out for and what to do if I had any problems. The team were so personable and welcoming that I would look forward to my trips in for a check-up. I’d love to commend the whole team from the front desk to the doctors and will be sure to join future studies.”

The study investigators recognise the important contribution that volunteers make to medical research and will make every effort to ensure their safety and wellbeing. Participants will be provided with an emergency contact number, monitored by study doctors 24/7. 

To sign up to the study or find out more information, you can visit: https://www.ovg.ox.ac.uk/studies/bivista/bristol.