Rationale: The live attenuated Bacillus Calmette-Guerin (BCG) vaccine protects against extrapulmonary infection with Mycobacterium tuberculosis and leprosy. It has been shown that vaccination with BCG also leads to nonspecific protective effects, e.g. reduced infant mortality as a result of less severe infections, stimulation of the immune system in patients with bladder cancer and higher cytokine production upon restimulation of macrophages with non-related infectious pathogens in vitro. However, because the live attenuated BCG vaccine cannot be used in immune compromised hosts, the investigators would like to determine whether similar protective non-specific effects can be induced by γ-irradiated BCG.