A new study has shed light on why the Bacillus Calmette Guérin (BCG) vaccine, widely used to protect against tuberculosis (TB), may also reduce the risk of Alzheimer’s disease. Researchers found that the vaccine appears to reprogram the immune system, creating long term changes that may help protect the brain from the neuroinflammation associated with Alzheimer’s and other forms of dementia.

The study suggests that the protective effect of the BCG vaccine may extend beyond tuberculosis by altering the body’s innate immune response through a process known as trained immunity. Researchers believe these immune changes could reduce chronic inflammation, a key factor implicated in the development and progression of Alzheimer’s disease.

Administered shortly after birth in many countries, the BCG vaccine is given intradermally (through the skin) to protect infants and young children against severe forms of tuberculosis. In addition to its established role in TB prevention, the vaccine has been investigated for several other therapeutic applications, including bladder cancer treatment, immune mediated diseases and protection against certain infections.

According to the World Health Organization (WHO), tuberculosis remains one of the world’s leading infectious diseases, with 10.8 million people developing TB and 1.25 million deaths recorded globally in 2023. Meanwhile, dementia affects more than 55 million people worldwide, with Alzheimer’s disease accounting for 60–70% of all dementia cases, making it one of the fastest growing public health challenges associated with ageing populations.

Researchers noted that previous observational studies had reported a lower incidence of Alzheimer’s disease among individuals who had received the BCG vaccine, but the biological mechanism behind this association remained unclear. The latest findings provide new evidence that immune system remodelling could play an important role in protecting brain health.

Healthcare experts cautioned that the findings do not suggest the BCG vaccine should currently be used as a preventive treatment for Alzheimer’s disease. They emphasized that further large scale clinical trials are needed to confirm the association, understand the duration of the protective effect and determine whether BCG vaccination could become part of future dementia prevention strategies.

The study adds to the growing body of research highlighting the connection between the immune system and neurodegenerative diseases, opening new avenues for developing therapies that target inflammation and immune regulation to delay or prevent Alzheimer’s disease.