• Fever (>38 ºC) within the past 24 hours • Suspicion of current active viral or bacterial infection • Expected vaccination during the first three months of the study period• 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

• Fever (>38 ºC) within the past 24 hours • Suspicion of current active viral or bacterial infection • Expected vaccination during the first three months of the study period• 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