BOSTON (CBS) – Researchers at Mass General Hospital announced a breakthrough in treating Type 1 Diabetes. In a long-term study released Thursday, patients in a clinical trial had their blood sugar levels restored to near normal, with lasting results.

Patients in the trial received two doses of the bacillus Calmette-Guerin (BCG) vaccine, an inexpensive vaccine that is widely used to prevent tuberculosis. Results were not immediate, but after three years, every patient, “showed an improvement in HbA1c to near normal levels – improvement that persisted for the following five years,” MGH said in a news release.

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“This is clinical validation of the potential to stably lower blood sugars to near normal levels with a safe vaccine, even in patients with longstanding disease,” said Dr. Denise Faustman, director of the MGH Immunobiology Laboratory, and the study’s senior author.

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“It’s the first trial showing long-term reversal of diabetes,” Faustman told the Boston Business Journal.

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A Phase 2 clinical trial is already underway. Researchers are hoping to mimic results from the first trial and zero in on the most effective dosing.