Study of the Immune Response to Yellow Fever Vaccine 17D in Adults Previously Vaccinated with 17D

What this Trial Is About

Researchers are investigating how adults who have previously received the yellow fever vaccine 17D respond to receiving the vaccine again. The study aims to understand how prior vaccination affects antibody levels and immune cell responses after re-vaccination. This research will help identify the antibody levels needed for effective protection and support future studies to improve yellow fever vaccination strategies. Participants will receive a single standard dose 0.5 mL of the yellow fever vaccine 17D given under the skin. The study involves one vaccination arm where all participants are re-vaccinated with the vaccine. This live-virus challenge approach allows researchers to measure immune responses over time and evaluate how well the vaccine boosts immunity. During the study, participants will provide medical and travel histories, blood samples before vaccination, and blood samples approximately every other day for 14 days after vaccination. They will also give a blood sample around 28 days post-vaccination. Participants will complete daily symptom diaries for 14 days and report any symptoms afterward. Researchers will monitor antibody levels, vaccine virus presence in the blood, and immune cell responses to assess vaccine effects and safety over the study period.

Immunogenicity of Yellow Fever Vaccine 17D in Adults With Prior 17D Vaccination