Inclusion Criteria:  Informed consent as documented by signature (see Informed Consent Form), Age ≥18 years, HIV-1 infection under continuous antiretroviral therapy for ≥1.5 years as requested in the Systems X Cohort, Current participation in the Swiss HIV Cohort Study and past participation in the Systems X Cohort.  Exclusion Criteria:  History of virological failure or treatment interruption at any time, defined as HIV-1 viral load >200c/ml at two consecutive measurements at least 4 weeks apart, CD4 T-cell count <200/μl at any time or <350/μl during the past 1 year Presence of other relevant immunosuppression according to the investigator in addition to HIV (a daily steroid intake of ≥20mg is considered clinically relevant), History of or current clinical evidence of active tuberculosis, Previous positive tuberculin skin test or tuberculosis INF-gamma release assay (Quantiferon-Test) within the past 10 years, Previous BCG-vaccination within the past 10 years, Known allergy to BCG vaccine or any of its components, Documented current febrile illness at screening or in the past 7 days. Women who are pregnant or breast-feeding