Actively Recruiting
A Human Experimental Medicine Study to Assess Whether the Gut Microbiota Regulates Specific and Non-specific Immune Responses to Vaccination
Led by South Australian Health and Medical Research Institute · Updated on 2025-12-10
348
Participants Needed
1
Research Sites
52 weeks
Total Duration
On this page
Sponsors
S
South Australian Health and Medical Research Institute
Lead Sponsor
R
Royal Adelaide Hospital
Collaborating Sponsor
AI-Summary
What this Trial Is About
Researchers are investigating how the gut microbiota influences immune responses to vaccines, focusing on the BCG vaccine and Yellow Fever vaccine in healthy adults aged 18 to 35. The study aims to understand whether reducing gut bacteria with antibiotics affects the protection these vaccines provide against specific infections and other immune challenges. The trial includes two sub-studies. In the first, participants receive either antibiotics or no antibiotics, followed by a BCG vaccine or placebo, with a second BCG vaccine given six months later. In the second sub-study, participants also receive antibiotics or not, followed by a BCG vaccine or placebo, then a Yellow Fever vaccine three months later. Vaccines are given by injection, and antibiotic courses last three days. Participants will undergo blood and stool sample collections at multiple times, including before and after vaccinations, with skin biopsies taken in the BCG sub-study to measure bacterial load. Blood is also tested for Yellow Fever viral load after vaccination. The study will monitor immune responses, microbiota diversity, and vaccine effects over five years, involving up to seven blood draws and three stool samples per participant.
CONDITIONS
Brief Title
Antibiotics and Vaccine Immune Responses Study
Who Can Participate
Eligibility Criteria
You may qualify if you...
- 18 to 35 years old
- Provided a signed and dated informed consent form
- BCG naive (for sub-study 1) and BCG and Yellow Fever vaccine naive (for sub-study 2)
- Willing to take a short course of antibiotics
- Willing to undergo a punch biopsy (for sub-study 1)
- Willing to have up to 7 blood samples and 3 stool samples collected over 5 to 7 months
- Not pregnant or intending to get pregnant during the study (pregnancy test offered to females)
You will not qualify if you...
- Previous BCG or Yellow Fever vaccination
- Previous Yellow Fever infection
- Evidence of latent tuberculosis infection
- Contraindications to BCG vaccine including bone marrow or lymphoid malignancies, immunodeficiencies, HIV infection
- Moderate or severe skin diseases such as eczema, dermatitis, or psoriasis
- Use of immunosuppressive or immune-modifying drugs including corticosteroids or biological agents
- Contraindications to Yellow Fever vaccine including thymus disease, immunocompromised status, history of haematopoietic stem cell transplant
- Severe allergic reactions to egg or chicken proteins
- Pregnant, breastfeeding, or planning pregnancy
- History of renal disease or insufficiency
- Tattoo obscuring BCG vaccination site
- History of severe allergic reaction or anaphylaxis to vaccination or antibiotics
- Chronic serious underlying illness
- Use of prescribed oral or intravenous antibiotics within 28 days prior to study visits 1 and 4, including specific antibiotics active against M. bovis
AI-Screening
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Your Study Journey
Duration - 2 to 4 weeks
Participants are screened for eligibility to participate in the trial.
1 visit (in-person)
Duration - 3 days
Participants are randomized to receive a 3-day course of antibiotics or no antibiotics and either a BCG vaccine or placebo injection in the left arm.
1 visit for randomization and vaccination
Duration - 2 weeks
Blood and stool samples are collected before vaccination, and blood samples are collected 2 weeks after BCG vaccination to assess immune responses. Stool samples are also collected prior to vaccination.
2 visits (blood and stool sample collections)
Duration - 3 to 6 months
Depending on the sub-study, participants receive a second vaccination challenge: the BCG vaccine 6 months after randomization (Sub-study 1) or the Yellow Fever vaccine 3 months after randomization (Sub-study 2). Blood samples are collected at specified days following Yellow Fever vaccination to monitor viral load.
1 vaccination visit plus 3 follow-up blood sample visits for Yellow Fever vaccine participants (days 3, 5, and 7 post-vaccination)
Duration - 2 weeks
For Sub-study 1, a punch skin biopsy is taken 2 weeks after the second BCG vaccine to assess bacterial load. Blood and stool samples continue to be collected as part of immune response monitoring.
1 biopsy visit and additional sample collection visits
Duration - 5 years
Participants are monitored over 5 years to assess bacterial load, immune responses, microbiota diversity, and viral load markers related to both vaccines.
Periodic visits for sample collection and assessments over 5 years
Trial Site Locations
Total: 1 location
1
South Australian Health and Medical Research Institute
Adelaide, South Australia, Australia, 5000
Actively Recruiting
Research Team
D
David Lynn
How is the study designed?
Study Type
INTERVENTIONAL
Masking
DOUBLE
Allocation
RANDOMIZED
Model
PARALLEL
Primary Purpose
BASIC_SCIENCE
Number of Arms
8
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