To assess the impact of T cell activation and CMV infection on the ability to mount an antigen-specific response following immunization with MVA85A, we examined mycobacterial antigen–specific IFN-γ responses and anti–Ag85A IgG in MVA85A-immunized infants at D28 following immunization with MVA85A. The gene discussed is IFNG; the disease is cytomegalovirus infection.