To investigate whether BCG has innate immune training effects in mature adults, a randomized pilot study of 40 adults >50 years of age in Guinea-Bissau will be conducted. The Bandim Health Project has conducted multiple large-scale RCT's and demographic surveillance. HIV negative adults >50 years of age in a recent HIV survey are eligible for the present study. They will be checked for clinical signs of TB and an HIV test will be preformed before enrolment. Exclusion criteria are BCG vaccination within the last 10 years, illness within the last 14 days, clinical signs of active TB, and/or a positive HIV test. Those who are overtly ill will be treated or referred to hospital if needed. Those with signs of TB will be referred to the TB hospital for further examinations. Those who have become HIV positive since they were tested in the survey will receive immediate counselling and be referred to the HIV clinic.