Can a century-old tuberculosis vaccine help protect the aging brain? According to new research from Mass General Brigham, the answer might be yes.
Scientists have discovered that the Bacillus Calmette-Guérin (BCG) vaccine appears to change the brain’s immune environment in ways that could help explain why previous studies have linked the vaccine with a lower risk of Alzheimer’s disease.
The findings were published in Communications Medicine.
The BCG vaccine has been used around the world for decades to protect against tuberculosis. Recently, researchers have become interested in its unexpected effects on the immune system.
Earlier studies suggested that BCG may improve the body’s defenses against several diseases beyond tuberculosis, but scientists wanted to know whether these immune changes also occur around the brain.
To investigate, the researchers studied 23 adults aged 55 years and older for one year. Some participants already showed biological signs of Alzheimer’s disease, while others did not. Throughout the study, the team collected blood samples and cerebrospinal fluid to monitor changes after BCG vaccination.
The results showed that the vaccine strengthened the activity of immune cells near the brain and spinal cord. These cells responded more effectively to immune challenges without causing extra inflammation. This is important because chronic inflammation is thought to contribute to the development of Alzheimer’s disease and other forms of dementia.
Another important finding involved amyloid-beta, one of the proteins most closely associated with Alzheimer’s disease. In people who did not yet have Alzheimer’s-related brain changes, levels of amyloid-beta fell in the fluid surrounding the brain while rising in the bloodstream.
Researchers believe this pattern may indicate that the protein was being cleared from the brain more effectively. However, people who already had Alzheimer’s-related pathology did not experience the same benefit, suggesting that earlier intervention may be more effective than treatment after disease has begun.
Lead researchers said these findings support the growing idea that the immune system plays an important role in maintaining brain health. Rather than affecting only infections, vaccines may also influence biological processes involved in aging and neurodegenerative disease.
The scientists emphasized that much more work remains. This was a small, open-label study without a placebo group, so the findings cannot prove that BCG prevents Alzheimer’s disease. Larger clinical trials will be needed to confirm the results and determine whether vaccination can actually delay memory loss or reduce dementia risk.
Even with these limitations, the study has several strengths. It carefully followed participants for an entire year and examined both blood and cerebrospinal fluid, providing valuable information about how the vaccine may influence the brain’s immune system.
Overall, the research offers promising evidence that an existing, well-known vaccine could someday become part of strategies aimed at preserving brain health before Alzheimer’s disease develops.
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Source: Mass General Brigham.
