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
Overview
- Phase
- Phase 2
- Intervention
- Not specified
- Conditions
- Typhoid Fever
- Sponsor
- University of Oxford
- Enrollment
- 112
- Locations
- 1
- Primary Endpoint
- Clinically or microbiologically proven typhoid infection
- Status
- Completed
- Last Updated
- 3 years ago
Overview
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.
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.
Investigators
Eligibility Criteria
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.
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:
Outcomes
Primary Outcomes
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 Outcomes
- Exploratory analysis of blood and faeces samples to investigate novel diagnostic methods for detecting Salmonella Typhi infection(From time of challenge until time of typhoid diagnosis (maximum time frame of 14 days))
- 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(From baseline (pre-vaccination) to final follow up visit at one year)
- Clinical manifestations of typhoid infection after typhoid challenge as determined by physical examination, participant symptom reporting and microbiological assays(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)
- Laboratory and high-throughput assays to measure gene expression and protein translation at baseline, post-vaccination and post-challenge time points(From baseline (pre-vaccination) to 28 days after challenge (total duration 2 months))
- Assessment of the number of participants reporting solicited local and systemic reactions, and unsolicited adverse events following vaccination with Vi-TCV(From time of vaccination until 7 days post-vaccination)