Investigating Enteric Fever – Salmonella Typhi and Paratyphi Challenge Study

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Brief Title

Investigating Enteric Fever - Salmonella Typhi and Paratyphi Challenge Study

Official Title

Investigating the Mechanisms and Determinants of Systemic and Mucosal Immunity to Salmonella Typhi and Salmonella Paratyphi A in naïve and Previously Exposed Individuals - A Challenge and Rechallenge Study

Brief Summary

      Enteric fever, an infection characterised by diarrhoea and rash, is most often caused by a
      bacteria called Salmonella enterica. After ingesting contaminated food or drink, the
      Salmonellae travel first to the gut, then the bloodstream, from where they can infect other
      parts of the body. Antibiotics are used to kill the bacteria, but with increasing rates of
      antibiotic resistance, this treatment is becoming less effective.

      Two Salmonella variants, Typhi and Paratyphi, cause over 30 million cases of enteric fever
      and more than 200,000 deaths per year, mostly in developing countries. While improved hygiene
      and sanitation should eventually eliminate enteric fever, reduction of the disease burden in
      the medium term is achievable through effective vaccination.

      Vaccines likely to be available for mass vaccination are effective only against those
      Salmonella strains that bear the Vi polysaccharide capsule protein. Strains that do not have
      these capsule proteins, or have no capsule, will not be affected by vaccination and could
      'fill' the space vacated by the capsulated strains. Indeed, enteric fever caused by S.
      Paratyphi A which does not carry the Vi protein, has risen during the past decade and
      accounts for more than half of all cases in some areas. Thus it is important that effective
      vaccines are available to protect against infection by both capsulated and noncapsulated
      Salmonella enterica. To develop such vaccines, we need a complete understanding of the human
      immune response to both types, including the contribution of immunity in the gut and the
      bloodstream, immune response to bacterial surface proteins, and the role of antibodies. How
      much cross-protection there is between the types of typhoidal Salmonellae after natural
      infection or vaccination is not known, but this is critical to vaccine development.

      This project aims to fill in the knowledge gaps highlighted, by fully characterising the
      infection process and immune response in enteric fever.

Detailed Description

      There are two main groups in this study. Firstly a group of 40 to 60 volunteers recruited
      from the community and not previously exposed to typhoidal Salmonella (part A); secondly a
      group of 20 to 60 volunteers from participants of previous challenge studies conducted by the
      Oxford Vaccine Group (part B).

      Participants in part A and B will be randomly allocated one-to-one to have either S. Typhi or
      S. Paratyphi. The dose of bacteria has been determined by previous challenge studies to give
      an attack rate of 60 to 75% in individuals naive to typhoidal Salmonella. The bacteria is
      then ingested as a drink with a bicarbonate buffer ('the challenge').

      In addition to these two groups, a preliminary study involving 3 to 10 participants to act as
      'negative controls' will be performed. They will ingest the bicarbonate drink but not be
      given S. Typhi or S. Paratyphi. This group is not randomised with part A or B, and is
      unblinded i.e. the participant will be aware that they are not drinking typhoidal Salmonella.
      The participants will have all the same procedures and investigations as those in part A and
      B, including endoscopy with biopsies, daily visits during the two week intensive phase, and a
      course of antibiotics.

      Prior to challenge, participants (from parts A, B and negative control group) will undergo
      endoscopy and tissue biopsies of the gut lining. This procedure will be repeated after the
      intensive phase and completion of a two week course of antibiotics.

      After challenge, participants will be reviewed daily for at least 14 days by study
      investigators. Samples of blood, stool, saliva and urine will be collected. Participants
      diagnosed with enteric fever will be treated immediately with antibiotics and samples will be
      taken as per the protocol. The participants who do not meet criteria for enteric fever will
      be treated with antibiotics on Day 14.

      Enteric fever is diagnosed if any of the following apply:

        1. A positive blood culture for S. Typhi or Paratyphi from 72 hours post-challenge,

        2. a positive blood culture for S. Typhi or Paratyphi within 72 hours post-challenge, with
           one or more signs/symptoms of enteric fever,

        3. persistent positive blood cultures (two or more blood cultures taken at least 4 hours
           apart) for S. Typhi or Paratyphi within 72 hours postchallenge, or

        4. oral temperature ≥ to 38°C persisting for 12 hours.

      A proportion of participants from Part A and B will be offered the optional procedures of
      enteric string tests (also called Enterotest) and/or Wireless Video Capsule Endoscopies
      (WCE). Participants consenting to these procedures will be selected sequentially until the
      quota has been filled for each group.

Study Type


Primary Outcome

Measure the attack rate after challenge with S. Typhi or S. Paratyphi A in naïve and previously challenged individuals.

Secondary Outcome

 To describe the human clinical response to S. Typhi or S. Paratyphi A in antigen-naïve and previously challenged individuals.


Typhoid Fever


Salmonella Typhi

Study Arms / Comparison Groups

 Part A
Description:  Cohort naive to typhoidal Salmonella challenged with either S. Typhi or S. Paratyphi


* Includes publications given by the data provider as well as publications identified by National Clinical Trials Identifier (NCT ID) in Medline.

Recruitment Information

Recruitment Status


Estimated Enrollment


Start Date

December 2014

Completion Date

May 26, 2022

Primary Completion Date

September 22, 2018

Eligibility Criteria

        Inclusion Criteria:

          -  In good health as determined by medical history, physical examination and clinical
             judgment of the investigators.

          -  Agree (in the Investigator's opinion) to comply with all study requirements, including
             capacity to adhere to good personal hygiene and infection control precautions.

          -  Agree to allow his or her General Practitioner (and/or Consultant if appropriate), to
             be notified of participation in the study.

          -  Agree to allow Public Health England to be informed of their participation in the
             study .

          -  Agree to give his or her close household contacts written information informing them
             of the participants' involvement in the study and offering them voluntary screening
             for S. Typhi or S. Paratyphi carriage.

          -  Agree to have 24-hour contact with study staff during the four weeks post challenge
             and are able to ensure that they are contactable by mobile phone for the duration of
             the challenge period until antibiotic completion.

          -  Have internet access to allow completion of the e-diary and real-time safety

          -  Agree to avoid antipyretic/anti-inflammatory treatment until advised by a study doctor
             or until at least 14 days after challenge.

          -  Willing to undergo endoscopy and biopsy.

        Exclusion Criteria:

          -  History of significant organ/system disease that could interfere with study conduct or

          -  Have any known or suspected impairment of immune function, alteration of immune
             function, or prior immune exposure that may alter immune function.

          -  Moderate or severe depression or anxiety as classified by the Hospital Anxiety and
             Depression Score at screening or challenge that is deemed clinically significant by
             the study investigators.

          -  Weight 50kg or less.

          -  Presence of implants or prosthesis.

          -  Have previously received any typhoid vaccine

          -  Any contraindication to elective upper GI endoscopy.

          -  More than one non-study related upper GI endoscopy within the last year.

          -  Anyone taking long-term medication that may affect symptom reporting or interpretation
             of the study results.

          -  Contra-indication to taking ciprofloxacin, azithromycin, trimethoprim/
             sulfamethoxazole and/or beta lactam antibiotics.

          -  Female participants who are pregnant or lactating.

          -  Female participants who are unwilling to ensure that they or their partner use
             effective contraception one month prior to challenge and continue to do so until two
             negative stool samples, a minimum of three weeks after completion of antibiotic
             treatment, have been obtained.

          -  Full-time, part-time or voluntary occupations involving clinical or social work with
             direct contact with young children (defined as those attending pre-school groups or
             nursery or aged under 2 years); clinical or social work with direct contact with
             highly susceptible patients or persons in whom typhoid or paratyphoid infection would
             have particularly serious consequences e.g. the elderly or infirm.

          -  Full time, part time or voluntary occupations involving commercial food handling.

          -  Close household contact with young children (defined as those attending pre-school
             groups, nursery or those aged less than 2 years), individual(s) who is (are)
             immunocompromised, scheduled elective surgery or other procedures requiring general
             anaesthesia during the study period.

          -  Participants who have participated in another research study involving an
             investigational product that might affect risk of typhoid or paratyphoid infection or
             compromise the integrity of the study within the 30 days prior to enrolment .

          -  Detection of any significantly abnormal results from screening investigations.

          -  Inability to comply with any of the study requirements.

          -  Any other social, psychological or health issues which, in the opinion of the study
             investigator, may put the participants or their contacts at risk because of
             participation in the study, adversely affect the interpretation of the primary
             endpoint data, or impair the participant's ability to participate in the study.

          -  Having been resident in an enteric fever endemic country for six months or more.




18 Years - 60 Years

Accepts Healthy Volunteers

Accepts Healthy Volunteers


Andrew Pollard, FRCPCH, PhD, , 

Location Countries

United Kingdom

Location Countries

United Kingdom

Administrative Informations



Organization ID

OVG 2014/01

Responsible Party


Study Sponsor

University of Oxford


 University of Liverpool

Study Sponsor

Andrew Pollard, FRCPCH, PhD, Principal Investigator, University of Oxford

Verification Date

January 2021