A drug that's been on the market for years is showing new promise for treating type 1 diabetes, the form of the disease that often strikes during childhood.

Researchers at Massachusetts General Hospital are launching a 5-year clinical trial of a vaccine that may not only treat the disease, but actually reverse it. The trial will investigate whether the BCG vaccination - a drug that has been used to prevent tuberculosis for decades - can improve type 1 diabetes in adults.

The research team led by Dr. Denise Faustman has already completed a successful trial showing that the BCG vaccine reversed advanced type 1 diabetes in mice and a phase I human clinical trial establishing the safety and potential of the drug.

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"We saw early signs that even at low doses of this vaccine the bad white blood cells that were killing the pancreas were killed, and also the good white blood cells that quiet down type 1 diabetes were up-regulated," Faustman told CBS Boston's Dr. Mallika Marshall.

Faustman's team is currently recruiting 150 patients to participate in the study.

Currently, people with type 1 diabetes must manage the condition by taking insulin on a regular basis and frequently monitoring their blood sugar.

Jennifer Sullivan, who was diagnosed as a teenager, has been living with the disease for 30 years. She says a treatment like this would allay fears shared by many diabetics: "The risk of complications, like blindness, amputations, kidney disease, heart disease, not seeing my son." Although Sullivan does not qualify to participate in the current round of testing, she hopes to take part in a future round.

Patients who join the clinical trial will receive two injections four weeks apart of either BCG or a placebo, and then a single injection annually for the next four years. They will be closely monitored throughout the entire period.

"We are trying to create a regimen that will treat even advanced disease," Faustman said.

So far the researchers have raised $19 million of the $25 million they will need to complete the study. Additional information about the clinical trial is available at http://www.faustmanlab.org.