Could a Century-Old Vaccine Help Improve Blood Sugar in Type 1 Diabetes?
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A vaccine first used against tuberculosis more than 100 years ago is being studied for a very different purpose: improving blood sugar control in people with long-standing type 1 diabetes.
In a small clinical trial, researchers at Massachusetts General Hospital found that repeated doses of the Bacillus Calmette-Guérin vaccine—better known as BCG—appeared to change the way certain white blood cells use energy. The metabolic change was associated with improved glucose control in adults who had developed type 1 diabetes during childhood.
The results are intriguing, but BCG is not approved as a treatment for type 1 diabetes. Larger, independent trials are needed before researchers can determine whether it is safe and effective for routine diabetes care.
What is the BCG vaccine?
BCG is an immunotherapy developed to protect against tuberculosis. It is widely used in many parts of the world, although it is not routinely given to most people in the United States. A form of BCG is also used to treat certain cases of bladder cancer.
Researchers have studied whether BCG can retrain parts of the immune system. Because type 1 diabetes is caused by an autoimmune attack on insulin-producing beta cells, scientists initially wondered whether the vaccine could calm or redirect that immune response.
What is different about this research?
The newer findings focus on metabolism inside white blood cells.
According to the researchers, some white blood cells in people with type 1 diabetes may rely more heavily on fat for energy instead of glucose. Repeated BCG vaccination appeared to shift those cells toward consuming more glucose. Researchers believe that increased glucose use by immune cells may contribute to lower glucose levels in the blood.
This proposed effect is notable because participants had long-standing type 1 diabetes and little or no remaining pancreatic insulin production. The study suggests that BCG’s potential effect may not depend entirely on restoring the pancreas.
What did the trial involve?
Adults with childhood-onset type 1 diabetes received multiple BCG injections over several years. Researchers used continuous glucose monitoring to evaluate changes in time in range and other glucose measurements.
The trial reported improvement in glucose control among treated participants. However, the study was small, the treatment took years to evaluate and the dosing schedule was very different from standard vaccination.
Those limitations are important. Small studies can produce encouraging signals that do not always hold up in larger trials. Researchers must also determine which patients, if any, are most likely to benefit.
BCG should not be used as a do-it-yourself diabetes treatment
People with type 1 diabetes should not seek BCG vaccination outside an appropriate clinical setting in an attempt to lower blood sugar. The vaccine can cause side effects and is not suitable for everyone, particularly some people with weakened immune systems.
BCG does not replace insulin. Stopping or reducing insulin without medical supervision can cause severe hyperglycemia and life-threatening DKA.
Why the study is still encouraging
The research explores a new way to think about type 1 diabetes: not only as a disease involving the pancreas and immune attack, but also as a condition involving how immune cells process energy.
Even if BCG itself does not become a standard treatment, understanding this pathway could point researchers toward other therapies that improve glucose control in new ways.
For now, proven tools remain essential. Insulin, continuous glucose monitoring, insulin pumps, nutrition, activity and regular medical care form the foundation of type 1 diabetes management. Direct Diabetes helps eligible patients receive prescribed CGMs, insulin pump supplies and other diabetes equipment through their insurance benefits.
This article is for educational purposes only. BCG is not FDA-approved to treat type 1 diabetes, and the research described here is preliminary.
