A BCG Challenge Model Study to Assess Anti-mycobacterial Immunity Induced by BCG and a Candidate TB Vaccine, MVA85A

The purpose of this study is to evaluate the BCG \'challenge\' model a four-arm study design has been chosen. Twelve subjects will be recruited into each arm of the study. Allocation of BCG-naïve volunteers to either group A or B, and BCG-vaccinated volunteers to either group C or D, will be performed on a one-to-one alternating basis. Subjects in each group will be challenged by BCG administered intradermally. Prior to challenge, pre-existing immunity to TB will be induced by vaccination with BCG, MVA85A, and both in combination (when compared to BCG- \& MVA85A-naïve individuals). BCG quantification will be assessed by analysing the tissue obtained in a punch biopsy of volunteers\' skin over the site of BCG \'challenge\' vaccination. Any reduction in BCG quantification between groups will then be correlated to existing (and future) laboratory assays of vaccine-induced immune responses in order to identify potential immunological correlates of protection.