The BCG – Bacille Calmette-Guérin – vaccine has been administered for almost a century to prevent tuberculosis or TB. It has U.S. Food and Drug Administration approval.
The phase 1 study conducted by researchers at Massachusetts General Hospital (MGH) concluded that:
"Long-term follow-up of participants in clinical trials of a generic vaccine to reverse advanced type 1 diabetes finds significant clinical benefits, including restoration of near-normal blood sugar levels. Three years after receiving two administrations of the bacillus Calmette-Guérin (BCG) vaccine four weeks apart, all members of a group of adults with longstanding type 1 diabetes showed an improvement in HbA1c to near normal levels – improvement that persisted for the following five years."