A vaccine that has been around for a hundred years for preventing the development of tuberculosis may eliminate type 1 diabetes, and an upcoming five-year trial could prove that.

The U.S. Food and Drug Administration has signed off on a mid-stage trial to test bacillus Calmette-Guerin (BCG) in 150 adults who are an advanced stage of the disease, according to a New York Daily News report.

About 5 percent of people — a total of three million — who have diabetes have the type 1 version, where the immune system destroys insulin-producing beta cells in the pancreas. The BCG vaccine works by tenmporarily raising levels of tumor necrosis factor (TNF), which can eliminate T cells in the blood of individuals who have the disease.

A small preliminary trial found that a couple of BCG injections that were given about a month apart eliminated these damaging T cells, and the body of the patients even returned to secreting insulin.

As a result of the promising results, lead author Dr. Denise Faustman, who is director of the Massachusetts General Hospital Immunobiology Laboratory in Boston, will start enrolling patients between the ages of 18 and 60 in a five-year trial as the next step in proving that the drug would result in a long-term cure for diabetes. The participants they will use will have low but a little bit of insulin secretion from the pancreas.

If the trial proves successful, it could be expanded to a larger number of patients.

The trial will focus on creating a regimen that will be effective against an advanced form of the disease.