A century-old tuberculosis vaccine may have a surprising role beyond preventing infectious disease, with new research suggesting that the Bacillus Calmette–Guérin (BCG) vaccine could influence immune responses linked to Alzheimer’s disease.
A recent study found that BCG vaccination may change the behaviour of immune cells around the brain and affect levels of amyloid beta, a protein associated with Alzheimer’s disease. The findings provide new insights into how the immune system and brain may interact in age-related neurological conditions.
Previous research has suggested that BCG vaccination could be linked to a lower risk of Alzheimer’s disease and may strengthen protection against infections beyond tuberculosis. However, scientists have been investigating the biological mechanisms behind these potential benefits.
Researchers followed older adults for one year after BCG vaccination, analysing blood and cerebrospinal fluid samples to examine changes in immune activity and proteins associated with brain health. The study included 23 adults aged 55 and above, including participants with and without biological indicators linked to Alzheimer’s disease.
The findings showed that BCG vaccination influenced immune cell activity by increasing their response to infection-related signals without raising overall inflammation levels. Since chronic inflammation is considered a factor in several age-related diseases, including Alzheimer’s, researchers believe these immune changes may provide important clues for future treatments.
The study also found changes in amyloid beta levels in blood and cerebrospinal fluid among participants without Alzheimer’s-related biological changes. However, similar changes were not observed in participants who already had these indicators, suggesting that the timing of vaccination may influence potential effects.
The BCG vaccine is one of the world’s most widely used vaccines and has traditionally been used to protect infants and young children against tuberculosis. It contains weakened strains of Mycobacterium bovis and is administered through an injection under the skin.
Scientists have increasingly studied BCG’s ability to create “trained immunity,” a process in which the body’s innate immune cells develop a stronger and more adaptable response to future threats. Researchers are now exploring whether these effects could also influence conditions associated with ageing and inflammation.
While the latest findings are promising, researchers emphasize that the study was small and that larger, controlled trials are needed before drawing conclusions about BCG’s role in preventing or slowing Alzheimer’s disease.
Future research will focus on whether BCG vaccination can help preserve brain health before significant Alzheimer’s-related changes develop. The findings highlight a growing understanding that vaccines may have effects beyond infectious disease protection and could influence broader aspects of human health.
