Vaccination against tuberculosis: is BCG more sinned against than sinner?

While extensive experimental studies of tuberculosis (Tb) have provided the foundation data for the discovery of cell-mediated immunity, there remains much to be disclosed about the critical pathways of immunity involved in this infectious process and the factors necessary to produce protective immunity. Studies on the aetiology and pathology of this disease have failed to elucidate the mechanisms of protective immunity. Although Tb research has been neglected for the past 30 years, the re-emergence of Tb worldwide as a significant zoonotic disease has re-focused research in this area. Scientific solutions for the control of Tb in man or domestic animals have not been found using empirical methods. Composite studies involving animal models of experimental infection will be necessary to critically evaluate vaccine efficacy and eludiate the basic immunological mechanisms involved in both disease and immunity. Available data which suggest that disease-related hypersensitivity and immunity are dissociable highlight the prospect that immunity to infection may be induced without compromising the continued need for ongoing systems of immunodiagnosis to exclude disease. In populations with a high prevalence of disease it is likely that a combination of immunodiagnosis, chemotherapy and immunoprophylaxis will be required to eradicate the disease.