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Vaccines Against Salmonella Typhi (VAST)

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT02324751
Recruitment Status : Active, not recruiting
First Posted : December 24, 2014
Last Update Posted : October 18, 2018
Information provided by (Responsible Party):
University of Oxford

Brief Summary:

Using an established model of human typhoid infection, whereby healthy adults are deliberately exposed to typhoid-causing bacteria, the investigators will determine how effective a new typhoid conjugate vaccine (Vi-TCV) is in preventing infection. The new typhoid vaccine will be compared with a control vaccine (meningococcal ACWY). The protective effect of a currently used typhoid polysaccharide vaccine (Vi-PS) will also be studied and compared with the control vaccine using this model of typhoid infection.

A second component of this study will involve vaccinating 15-20 participants with Vi-PS. Serum will be obtained prior to vaccination and 4-6 weeks after vaccination. The post-vaccination serum will be pooled and used to create an anti-Vi IgG serum standard.

Condition or disease Intervention/treatment Phase
Typhoid Fever Enteric Fever Biological: Vi-TCV Biological: Vi-PS Vaccine Biological: Control (Men ACWY) Phase 2

Detailed Description:

Typhoid fever is an infection caused by a bacterium, Salmonella Typhi, that only causes disease in humans. It is transmitted faecal-orally and causes more than 22 million infections every year in developing countries, such as areas of Asia, Africa and South America, where access to clean drinking water and sanitation facilities is limited. Although typhoid fever is treatable with effective antibiotics, there are more than 200,000 deaths every year in these resource-limited regions.

Salmonella Typhi could be eradicated but improving sanitation and living conditions in endemic regions is difficult. Vaccination to prevent the transmission of Salmonella Typhi could significantly reduce the burden of disease. The currently licensed typhoid vaccines are only moderately effective in preventing infection in people who have been immunised and no vaccines are licensed for use in young children. Novel typhoid vaccines have been developed to overcome these problems, but more research and information is needed to study how well these vaccines work before they can be routinely used.

This study proposes to investigate the protective effect of a novel typhoid vaccine (typhoid Vi polysaccharide capsule - tetanus toxoid conjugate vaccine) using a human challenge model of typhoid infection. Healthy adults will be vaccinated with the novel typhoid vaccine, a currently used typhoid vaccine (Vi polysaccharide capsule vaccine) or a control vaccine. One month after vaccination, participants will be exposed to live Salmonella Typhi by drinking a solution containing the bacteria. Participants will then be closely monitored to determine which participants develop infection and which are protected. In addition to assessing the protective effect of conjugated and unconjugated typhoid vaccines, the effect the vaccines have on the immune system and on the clinical course of typhoid infection will also be studied.

It is hoped that the knowledge gained from this study will contribute to the use of vaccines against Salmonella Typhi to help control this preventable disease.

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 112 participants
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single (Participant)
Primary Purpose: Prevention
Official Title: A Phase IIb, Observer-blind, Randomised Controlled Trial to Assess the Immunogenicity and Protective Efficacy of Vi Conjugated (Vi-TCV) and Unconjugated (Vi-PS) Polysaccharide Vaccines in Preventing Typhoid Infection Compared to a Control Vaccine (Meningococcal ACWY), Using a Human Challenge Model of Typhoid Infection
Study Start Date : September 2015
Actual Primary Completion Date : December 2, 2017
Estimated Study Completion Date : December 2018

Resource links provided by the National Library of Medicine

MedlinePlus related topics: Fever

Arm Intervention/treatment
Experimental: Vi-TCV
Single intramuscular injection
Biological: Vi-TCV
Each 0.5mL vaccine dose contains 25μg of purified Vi capsular polysaccharide (S. Typhi Ty2 strain) conjugated to non-toxic tetanus toxoid. The vaccine will be administered 28 days prior to typhoid challenge
Other Name: Typbar-TCV

Active Comparator: Vi-PS Vaccine
Single intramuscular injection
Biological: Vi-PS Vaccine
Each 0.5 mL vaccine dose contains 25 μg of purified Vi capsular polysaccharide (S. Typhi Ty2 strain). The vaccine will be administered 28 days prior to typhoid challenge
Other Name: TYPHIM Vi

Control (Men ACWY)
Single intramuscular injection
Biological: Control (Men ACWY)
Each vaccine dose contains N. meningitidis oligosaccharides (10μg MenA oligosaccharide, 5μg of each of MenC, Men Y and MenW-135 oligosaccharides) conjugated to 32.7 μg to 64.1μg Diphtheria CRM197 protein with residual formaldehyde dose less than 0.30μg. The vaccine will be administered 28 days prior to typhoid challenge
Other Name: MENVEO

Primary Outcome Measures :
  1. Clinically or microbiologically proven typhoid infection [ Time Frame: Up to 14 days after typhoid challenge dose administration ]
    Clinical (fever >38 degrees for more than 12 hours) or microbiologically (blood culture positive) proven typhoid infection following oral challenge with Salmonella Typhi.

Secondary Outcome Measures :
  1. Clinical manifestations of typhoid infection after typhoid challenge as determined by physical examination, participant symptom reporting and microbiological assays [ Time Frame: Clinical signs and solicited symptoms occurring during the 21 day period after challenge; microbiological assays and unsolicited symptoms followed up over the course of one year ]
    In particular comparing control and typhoid vaccination groups regarding time to onset of symptoms, duration of illness, symptom severity, time to onset of bacteraemia, time to onset of stool shedding, and inflammatory response after typhoid challenge

  2. Host immune responses (including Geometric Mean Titres of Salmonella Typhi antigen specific antibodies, antigen specific cell frequencies) at baseline, post-vaccination and post-typhoid challenge time points [ Time Frame: From baseline (pre-vaccination) to final follow up visit at one year ]
  3. Laboratory and high-throughput assays to measure gene expression and protein translation at baseline, post-vaccination and post-challenge time points [ Time Frame: From baseline (pre-vaccination) to 28 days after challenge (total duration 2 months) ]
    To assess variation in genomic response to vaccination with Vi-TCV, Vi-PS and control vaccine and subsequent Salmonella Typhi challenge

  4. Exploratory analysis of blood and faeces samples to investigate novel diagnostic methods for detecting Salmonella Typhi infection [ Time Frame: From time of challenge until time of typhoid diagnosis (maximum time frame of 14 days) ]
  5. Assessment of the number of participants reporting solicited local and systemic reactions, and unsolicited adverse events following vaccination with Vi-TCV [ Time Frame: From time of vaccination until 7 days post-vaccination ]

Other Outcome Measures:
  1. Producing an anti-Vi IgG serum standard from volunteers vaccinated with Vi-PS (Vi polysaccharide vaccine) [ Time Frame: From time of vaccination until 4-6 weeks post-vaccination ]
    Sera obtained at baseline and 4-6 weeks post-vaccination, followed by pooling of post-vaccination sera to form an anti-Vi IgG serum standard

Information from the National Library of Medicine

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Ages Eligible for Study:   18 Years to 60 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

Participants must satisfy all of the following criteria to be considered eligible for the study:

  • Agree to give informed consent for participation in the study.
  • Aged between 18 and 60 years inclusive at time of vaccination.
  • In good health as determined by medical history, physical examination and clinical judgment of the study team.
  • Agree (in the study team'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 study staff to contact his or her GP to access the participant's vaccination records.
  • Agree to allow Public Health England to be informed of their participation in the study.
  • Agree to give his or her close contacts written information informing them of the participant's involvement in the study and offer them voluntary screening for S. Typhi 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 monitoring.
  • Agree to avoid antipyretic/anti-inflammatory treatment from the time of challenge (Day 0) until advised by a study doctor or until 14 days after challenge.
  • Agree to provide their National Insurance/Passport number for the purposes of TOPS registration and for payment of reimbursement expenses.

Exclusion Criteria:

The participant will not be enrolled if any of the following apply:

  • History of significant organ/system disease that could interfere with trial conduct or completion. Including, for example, but not restricted to: Cardiovascular, respiratory, haematological, endocrine, Renal/bladder, biliary tract, gastro-intestinal, neurological, metabolic, autoimmune or infectious disease. Or Psychiatric illness requiring hospitalisation or known or suspected drug and/or alcohol misuse
  • Have any known or suspected impairment of immune function, alteration of immune function, or prior immune exposure that may alter immune function to typhoid infection
  • 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 doctors .
  • Weight less than 50kg
  • Presence of implants or prosthesis.
  • Anyone taking long-term medication that may affect symptom reporting or interpretation of the study results.
  • Contraindication to ciprofloxacin or macrolide antibiotics.
  • Female participants who are pregnant, lactating or 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 2 weeks after completion of antibiotic treatment, have been obtained.
  • Occupations involving:

    • Direct contact with young children attending pre-school groups or nursery or aged under 2 years, or
    • Direct contact with highly susceptible patients or persons in whom typhoid infection would have particularly serious consequences (unless willing to avoid work until demonstrated not to be infected with typhoid in accordance with guidance from Public Health England)
  • 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)
    • Immunocompromised individuals
  • 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 within the 30 days prior to enrolment
  • Detection of any abnormal results from screening investigations (at the clinical discretion of the study team).
  • Inability to comply with any of the study requirements
  • Any other social, psychological or health issues which, in the opinion of the study staff, may

    • Put the participant or their contacts at risk because of participation in the study,
    • Adversely affect the interpretation of the primary endpoint data,
    • Impair the participant's ability to participate in the study.
  • Having previously received any typhoid vaccine
  • Having been resident in an enteric fever endemic country for 6 months or more.
  • Have previously been diagnosed with laboratory-confirmed typhoid or paratyphoid infection or been given a diagnosis compatible with enteric fever.
  • Have participated in previous typhoid or paratyphoid challenge studies
  • Have received vaccination with tetanus toxoid containing vaccine within the past 12 months.
  • Have any history of allergy to vaccine components
  • Have a prolonged corrected QT interval (>450 milliseconds) on ECG screening

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT02324751

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United Kingdom
Centre for Clinical Vaccinology and Tropical Medicine
Oxford, Oxfordshire, United Kingdom, OX3 7LE
Sponsors and Collaborators
University of Oxford
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Principal Investigator: Andrew J Pollard, FRCPCH, PhD Oxford Vaccine Group, The University of Oxford

Additional Information:
Publications automatically indexed to this study by Identifier (NCT Number):
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Responsible Party: University of Oxford Identifier: NCT02324751     History of Changes
Other Study ID Numbers: OVG 2014/08
First Posted: December 24, 2014    Key Record Dates
Last Update Posted: October 18, 2018
Last Verified: February 2018
Additional relevant MeSH terms:
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Typhoid Fever
Body Temperature Changes
Signs and Symptoms
Salmonella Infections
Enterobacteriaceae Infections
Gram-Negative Bacterial Infections
Bacterial Infections
Immunologic Factors
Physiological Effects of Drugs