A vaccine developed more than a century ago to fight tuberculosis may offer a surprising new benefit, helping treat Type 1 diabetes.

Dr. Denise Faustman of Massachusetts General Hospital says the BCG vaccine appears to retrain the immune system in a way that helps the body regulate blood sugar.

“This drug does immuno-stimulation and in that process it’s remolding how genes are expressed,” Dr. Faustman said.

According to Faustman, the drug helps cells in diabetes patients learn to use sugar instead of fat. After two long-term adult trials and the start of a pediatric trial, her team hopes to show that the treatment can lower blood sugar for months or even years.

Researchers say more study is needed, but early results suggest the century-old vaccine could become a powerful new tool in managing Type 1 diabetes.