Antibiotics and Vaccine Immune Responses Study — AVIRS  

Vaccine Response Impaired Clinical Trial

Official title: A Human Experimental Medicine Study to Assess Whether the Gut Microbiota Regulates Specific and Non-specific Immune Responses to Vaccination

Status Recruiting

Clinical Trial Summary

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?

Clinical Trial 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. ;

Related Conditions & MeSH terms

• Vaccine Response Impaired

• NCT number: NCT06148025
• Study type: Interventional
• Source: South Australian Health and Medical Research Institute
• Contact: David Lynn
• Phone: +61 8 8128 4053
• Email: david.lynn@sahmri.com
• Status: Recruiting
• Phase: Phase 4
• Start date: November 23, 2023
• Completion date: October 2028