Study to Understand How Gut Bacteria Affect Immune Responses to BCG and Yellow Fever Vaccines In Healthy Adults Aged 18 to 35

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.

Antibiotics and Vaccine Immune Responses Study