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About
The goal of this clinical trial is to examine immune responses to the BCG vaccine in healthy adults who have, or who have not, taken antibiotics to deplete their gut bacteria prior to vaccination.
The main question it aims to answer is: does depletion of the gut microbiota lead to impaired BCG-induced protection against specific and non-specific to challenges to the immune system?
Full description
The study is divided into two sub-studies. The first sub-study (BCG re-challenge) is an experimental medicine study in 168 healthy participants to determine if depletion of the gut microbiota leads to impaired BCG-induced protection against a subsequent Mycobacterium bovis BCG intradermal challenge.
The second sub-study (Yellow Fever vaccine) has a very similar experimental design to the first but will determine if depletion of the gut microbiota leads to impaired BCG-induced protection against other infections. To assess this, participants in this sub-study (n=180) will be re-challenged after 3 months with a live attenuated viral vaccine, the Yellow Fever vaccine, which induces a mild viremia.
In both sub-studies, participants will initially be randomised to receive a 3 day course of antibiotics or none (comparator group). The two groups in each sub-study will be randomised again to receive either BCG vaccine or 0.9% NaCl placebo injection in the left arm.
BCG re-challenge sub-study (Sub-study 1): Six months following randomisation, all participants will receive a BCG vaccine challenge in the right arm. A punch skin biopsy will be taken of this challenge site 2 weeks after the challenge to assess M. bovis BCG bacterial load in the skin.
Yellow Fever vaccine sub-study (Sub-study 2): Three months following randomisation, all participants will receive a Yellow Fever vaccine challenge in the right arm. Blood samples will be collected from Yellow Fever vaccinated participants at day 3, 5 and 7 following Yellow Fever vaccine challenge to quantify Yellow Fever viral load in blood.
All participants in both sub-studies will have blood samples collected at randomisation, before each vaccination, 2 weeks after each BCG vaccination and in the Yellow Fever vaccine sub-study at day 3, 5 and 7 following Yellow Fever vaccination. Stool samples will be collected prior to randomisation, and prior to each vaccination.
Enrollment
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Inclusion criteria
Exclusion criteria
Previous BCG or YF vaccination
Previous YF infection
Evidence of latent TB infection (LTBI) (assessed through a questionnaire) (IGRA to confirm if needed)
People with contraindications for BCG vaccination:
People with contraindications to YF vaccination:
Pregnant or breastfeeding or planning to become pregnant
History of renal disease/insufficiency
Tattoo obscuring BCG vaccination site(s)
Any history of severe allergic reaction or anaphylaxis to vaccination
People with chronic serious underlying illness
Have received any prescribed oral or intravenous antibiotic in the 28 days prior to study visits 1 and 4 (including isoniazid, rifampicin, streptomycin and ethambutol as these particular antibiotics have activity against M. bovis)
Primary purpose
Allocation
Interventional model
Masking
348 participants in 8 patient groups
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Central trial contact
David Lynn
Data sourced from clinicaltrials.gov
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