BCG vaccine changes Alzheimer’s biomarkers in pilot study

A yearlong pilot study has found that the tuberculosis vaccine BCG can alter the immune environment surrounding the brain and shift key biomarkers associated with Alzheimer’s disease, offering a potential biological explanation for previously observed links between the vaccine and reduced dementia risk. The research, led by investigators at Mass General Brigham and published in Communications Medicine, provides early human evidence that the vaccine’s effects reach the central nervous system.

The study involved two related, open-label clinical trials with 23 adults aged 55 and older. Twelve participants had no biomarker evidence of Alzheimer’s-related pathology, while 11 others had such pathology along with mild cognitive impairment or mild-to-moderate Alzheimer’s disease. All participants received two intradermal BCG vaccinations one month apart and were followed for 12 months, with regular samples taken of their blood and cerebrospinal fluid.

Researchers reported that BCG vaccination induced persistent changes in immune cells within the cerebrospinal fluid, enhancing their innate responsiveness to other immune challenges. This effect, a hallmark of a phenomenon known as...