A new set of pilot trials found that BCG, the tuberculosis (TB) vaccine, shifted several brain-related biomarkers in older adults without Alzheimer's pathology. But the same shifts did not appear in people who already had Alzheimer's biomarker changes, so the studies do not show the vaccine slows Alzheimer's progression. BCG (Bacillus Calmette–Guérin) is a live, weakened TB vaccine. The two one-year, open-label pilot trials, published in *Communications Medicine* in 2026 by a Mass General Brigham/Harvard team, are worth understanding for what they actually measured — and what they cannot yet claim.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- What the new trials actually found
- Why this doesn't prove the vaccine slows Alzheimer's
- Is BCG approved for Alzheimer's? No.
- Where the Alzheimer's idea came from
- What a reader can practically do now
- Frequently Asked Questions
What the new trials actually found
The researchers enrolled just 23 adults aged 55 and older. As the Mass General Brigham team reported, 12 had no Alzheimer's-related pathology and 11 already did. Each person received two intradermal BCG doses one month apart and was followed for a year. In the participants without Alzheimer's pathology, amyloid-β in the cerebrospinal fluid (the clear fluid around the brain and spinal cord) fell, while amyloid-β in the blood rose.
Researchers read this pattern as a possible sign of improved clearance of amyloid from the brain. Amyloid-β is a protein that clumps into the plaques associated with Alzheimer's. BCG also produced durable "trained immunity" in immune cells within the cerebrospinal fluid and reset multiple proteins in the central nervous system. In plain terms, the vaccine appeared to change how the brain's immune environment signals.
Why this doesn't prove the vaccine slows Alzheimer's
The title's phrase "progression markers" needs a hard caveat. The biomarker shifts seen in healthy participants did not occur in the people who already had Alzheimer's biomarker evidence. That is the exact group where "slowing progression" would matter most. The study authors are direct about the limits.
They state the results do not show that BCG prevents or slows Alzheimer's. The trials were small, open-label, and had no placebo group — three features that make firm conclusions impossible. Open-label means everyone knew they were getting the vaccine. Without a placebo comparison, researchers cannot rule out chance, natural variation, or the effect of simply being studied and monitored closely for a year.
Is BCG approved for Alzheimer's? No.
BCG is a TB vaccine, and its approved uses are narrow. In the United States, the CDC notes that BCG is FDA-approved only for people at risk of tuberculosis and, in a different formulation, as a bladder-instilled therapy for early bladder cancer.
There is no approval to use BCG for preventing, treating, or slowing Alzheimer's. Asking a doctor for the TB vaccine as a dementia treatment is not a supported option today. Any use for brain health remains experimental and confined to research settings.
Where the Alzheimer's idea came from
This research did not appear from nowhere. Earlier studies of bladder cancer patients — who receive BCG directly into the bladder — found they had a lower later risk of dementia. A 2024 systematic review and meta-analysis summarized that association.
That link pointed to "trained innate immunity" as a possible mechanism: the idea that BCG tunes the immune system broadly, in ways that might affect the brain. The new pilot trials were designed to look for biomarker signals that fit this theory. An association in cancer patients, though, is not proof that the vaccine protects the brain.
What a reader can practically do now
For patients, families, and caregivers, the honest answer is to watch this space rather than act on it. Here is how to keep perspective: A separate randomized trial, NCT06078891, is now testing whether BCG changes Alzheimer's biomarkers using a stronger design. Randomized trials with a control group are the type of evidence that could move this from intriguing to actionable.
- Do not seek BCG for dementia prevention. It is not approved for that use, and the evidence does not support it.
- Treat headlines about "progression markers" cautiously; the effect was absent in people who already had Alzheimer's pathology.
- Follow the science through rigorous trials, not pilot studies.
Frequently Asked Questions
Did the TB vaccine slow Alzheimer's in this study?
No. The trials measured biomarkers, not disease progression, and the shifts were absent in participants who already had Alzheimer's pathology.
Can I get BCG to lower my dementia risk?
Not as an approved treatment. BCG is approved only for TB risk and early bladder cancer, so any brain-health use stays experimental.
What would stronger evidence look like?
A randomized, placebo-controlled trial. One such study, NCT06078891, is now testing whether BCG changes Alzheimer's biomarkers.
