A potential subject who meets any of the following criteria will be excluded from participation in this study: Fever (>37,5 ºC) within the past 24 hours Suspicion of current active viral or bacterial infection Expected vaccination during the study period, independently of the type of vaccination. Severely immunocompromised subjects. This exclusion category comprises: a) subjects with known infection by the human immunodeficiency virus (HIV-1), b) neutropenic subjects with less than 500 neutrophils/mm3, c) subjects with solid organ transplantation, d) subjects with bone marrow transplantation, e) subjects under chemotherapy, f) subjects with primary immunodeficiency, g) severe lymphopenia with less than 400 lymphocytes/mm3, h) treatment with any immunosuppressant drugs such as anti-cytokine therapies, and treatment with oral or intravenous steroids defined as daily doses of 10mg prednisone or equivalent for longer than 3 months, or probable use of oral or intravenous steroids in the following four weeks Active solid or non-solid malignancy or lymphoma within the prior two years Active participation in another research study that involves BCG administration

A potential subject who meets any of the following criteria will be excluded from participation in this study: Fever (>37,5 ºC) within the past 24 hours Suspicion of current active viral or bacterial infection Expected vaccination during the study period, independently of the type of vaccination. Severely immunocompromised subjects. This exclusion category comprises: a) subjects with known infection by the human immunodeficiency virus (HIV-1), b) neutropenic subjects with less than 500 neutrophils/mm3, c) subjects with solid organ transplantation, d) subjects with bone marrow transplantation, e) subjects under chemotherapy, f) subjects with primary immunodeficiency, g) severe lymphopenia with less than 400 lymphocytes/mm3, h) treatment with any immunosuppressant drugs such as anti-cytokine therapies, and treatment with oral or intravenous steroids defined as daily doses of 10mg prednisone or equivalent for longer than 3 months, or probable use of oral or intravenous steroids in the following four weeks Active solid or non-solid malignancy or lymphoma within the prior two years Active participation in another research study that involves BCG administration