BCG Vaccine Trials Show Immune Reprogramming and Altered Alzheimer's Biomarkers

Two small open-label clinical trials have produced intriguing results: the century-old tuberculosis vaccine BCG (Bacillus Calmette-Guérin) appears to reprogram central nervous system immunity and alter biomarkers associated with Alzheimer's disease. Participants receiving BCG showed changes in cerebrospinal fluid immune markers and shifts in Alzheimer's-related proteins, suggesting the peripheral immune stimulus reaches and modifies brain inflammation. The findings align with emerging evidence that training innate immunity—making it more responsive through epigenetic changes—may influence neurodegenerative processes. However, caution is warranted: these were small, open-label (non-blinded, non-placebo-controlled) trials measuring surrogate biomarkers, not clinical outcomes like cognition or disease progression. The mechanism isn't fully understood, and it's unclear whether biomarker changes translate to clinical benefit or harm. Still, the results support a testable hypothesis that immune reprogramming could be therapeutically relevant for Alzheimer's, and warrant properly controlled trials. If validated, this would represent a fundamentally new approach—leveraging immune training rather than targeting amyloid or tau directly.