Is the incidence of AIDS-associated Mycobacterium avium-intracellulare disease affected by previous exposure to BCG, M. tuberculosis or environmental mycobacteria?

The incidence of disease due to Mycobacterium avium-intracellulare (MAI) in AIDS patients varies from region to region. It has been previously postulated that this difference is the result of a protective effect of neonatal BCG vaccination. The basis of this hypothesis is examined and it is further postulated that a similar protective effect may be afforded by self-limiting tuberculosis in childhood and by exposure to certain environmental mycobacteria. The possibility of developing vaccination strategies to limit the incidence of AIDS-related MAI disease thus requires consideration.