Development of a Vaccine against Salmonella Paratyphi A (VASP)

You are invited to take part in a study to investigate whether a novel vaccine can prevent paratyphoid fever. The study is being run by the Oxford Vaccine Group which is part of the University of Oxford and is funded by the Medical Research Council. If you are aged 18 to 55 years old, and in good health, then you may be eligible to take part in the study. We will provide reimbursement for your time, inconvenience, and travel. Participants will receive up to £2965 if they remain in the study for the entire period.

The total study participation time is 14 months, and you will be required to travel to Oxford for the study visits.



Salmonella Paratyphi A is a bacteria that can cause a disease called enteric fever. Although it is from the same family as the Salmonella bacteria that cause gastroenteritis in the UK, it is quite different. Paratyphoid infection is most common in poor communities in Asia with inadequate sanitation and limited access to safe water.

The bacteria are spread when infected individuals’ faeces contaminate food and water sources. Symptoms of infection include headache, fever, chills and general aches and pains. If not treated properly paratyphoid infection can lead to severe complications and even death.

There are currently no licensed vaccines against Salmonella Paratyphi A. There are vaccines in development however designing a vaccine is difficult as it is not yet understood exactly what immune responses may protect individuals from disease.

One of the vaccines in development is an oral vaccine called CVD 1902. A previous study run by the Oxford Vaccine Group suggested that having a previous infection with Salmonella Paratyphi A might protect an individual from further infection. The University of Maryland in Baltimore, USA have developed a weakened (attenuated) form of Salmonella Paratyphi A bacteria to act as a vaccine to protect individuals without causing them disease.

In this study we hope to see if an experimental vaccine can protect against Salmonella Paratyphi A infection and to understand which parts of the immune response may be important in preventing disease. We hope that the knowledge gained from this trial will help in the development of vaccines and make paratyphoid fever a preventable disease.

To do this we will be giving participants either two doses of the vaccine or two doses of placebo. One month after the second dose, we will be deliberately exposing participants to live Salmonella Paratyphi A bacteria. We do this by asking them to swallow a solution containing the bacteria. We will then treat participants as soon as they show any symptoms of infection. This process is known as a ‘challenge’ and has been undertaken by participants in previous Oxford Vaccine Group studies since 2011.

We know that by giving a specific dose of Salmonella Paratyphi A approximately 60% of people exposed to the bacteria will develop paratyphoid infection. By using this very controlled setting to expose people to Salmonella Paratyphi A we can test vaccines to determine how well they protect against infection. This type of study has already been performed for Salmonella Typhi, a close relative of Salmonella Paratyphi A which causes the same disease. If fewer people are infected with paratyphoid after receiving the investigational vaccine (less than 60 to 70%), then we can show that the vaccine protects against paratyphoid infection. The group receiving the placebo will receive the carrier solution for the vaccine but with no bacteria in the carrier solution.

In addition, we will be able to study how the immune system responds to this paratyphoid vaccine and how this helps to prevent paratyphoid infection. This will add to our general understanding of paratyphoid disease and vaccine development.

The Oxford Vaccine Group, University of Oxford, is based in the Centre for Clinical Vaccinology and Tropical Medicine at the Churchill Hospital site.

Further Information

If you would like to find out more, please read the Study Information Booklet and if you are interested in joining the study, please visit where you can access the screening questions and register your interest.

If you would like any further information regarding the study, please contact us on:

Email, Tel: 01865 611400

Kind Regards,

The Oxford Vaccine Group


Thank you, but unfortunately you need to be within easy traveling distance of a study site.


Unfortunately we can’t consider you for this trial until you have read the Participant Information Leaflet.


Thank you for your interest in the trial. In order to help manage the risks of COVID-19 we are trying to minimise the time volunteers spend at our screening visits. To help with this, we would like to gather information about your medical history here. This will be used to help decide if you are eligible to take part in the study. Giving your consent means that you are happy for us to store and use your personal information for the purposes of this trial. Information will be stored in accordance with the UK GDPR and Data Protection Act. Further information can be found at:


Thank you for your interest. Unfortunately, you are not eligible to join this trial. Your data has not been stored. If you are interested in hearing more about our other studies, you can sign up to our newsletter here


Thank you for your interest in joining this study. We will be in touch to discuss further arrangements with you.

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