August 4, 2026, 5:51 pm | Read time: 4 minutes
Can a well-known vaccine play an unexpected role in the fight against Alzheimer’s? Researchers have delved into this question and made observations that could provide new impetus for dementia research. Many questions remain unanswered, but the results of a new pilot study warrant further investigation.
An international team of scientists investigated whether the tuberculosis vaccine BCG can influence early biological processes associated with Alzheimer’s. The researchers followed 23 adults aged at least 55 over a period of one year. All participants received two BCG vaccinations one month apart. Twelve of the subjects were considered healthy, while eleven already showed biological changes regarded as typical Alzheimer’s biomarkers. As part of the study, the scientists analyzed blood samples, cerebrospinal fluid samples, and various disease-relevant markers.1
BCG stands for “Bacillus Calmette-Guérin.” The live vaccine was originally developed to prevent tuberculosis. Additionally, it is now used as an immunotherapy for certain forms of bladder cancer because it specifically stimulates the immune system. This effect has now become a focal point in Alzheimer’s research.
Changes in Healthy Study Participants
According to the researchers, the concentration of the protein amyloid-beta, typical of Alzheimer’s, significantly decreased in the cerebrospinal fluid of healthy participants. At the same time, there were indications of a long-term activation of certain immune cells. This effect was not observed in participants who already exhibited Alzheimer’s biomarkers. The authors of the study see this as a possible indication that BCG could influence the immune response in the brain.
The scientists explain this with the principle of so-called trained immunity. In this process, certain immune cells remain on heightened alert for an extended period and respond more quickly to threats. According to the authors, these cells could thus help more efficiently in the brain to break down harmful protein deposits like amyloid. However, whether this biological effect actually reduces the risk of Alzheimer’s or alters the course of the disease cannot be determined based on the small pilot study.
Other Vaccinations Also Show Interesting Connections
For Prof. Dr. Christoph Kleinschnitz, director of the Department of Neurology at the University Hospital Essen, the results fit into already known observations. “I find the results interesting, and they align with earlier vaccination studies on shingles and flu, which also showed that these vaccinations can significantly reduce the risk of developing Alzheimer’s in healthy people.” According to him, there are now even initial indications of possible benefits for those already affected. “For example, dementia patients vaccinated against shingles died less frequently during the study than unvaccinated dementia patients.”
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Why Vaccinations Could Protect the Brain
How vaccinations might exert a protective effect on the brain is not yet fully understood. Kleinschnitz explains: “It is likely that certain immune cells–so-called phagocytes–in the blood and brain can better remove harmful protein deposits. They are activated by the vaccination.”
This connection has been particularly intensively studied in vaccinations against shingles. The neurologist explains: “With the herpes zoster virus, it is such that this virus remains in the nervous system for life, and each outbreak can trigger an inflammatory reaction that could damage the brain in the long term and exacerbate dementia. The vaccination reduces these virus outbreaks.”
Experts Urge Caution
Despite the promising observations, both the study authors and Prof. Dr. Kleinschnitz emphasize the limitations of the research. The work was designed as a pilot study and was primarily intended to explore biological mechanisms in more detail. Statements about actual protection against Alzheimer’s or effective treatment of the disease cannot currently be derived from it. Therefore, there can be no talk of a vaccination against Alzheimer’s based on the current state of research. The results provide more starting points for larger studies that should examine the possible connection between BCG vaccination, the immune system, and Alzheimer’s more closely.