NEW YORK (CBSNewYork) – There’s a potential breakthrough in diabetes treatment that could help millions of people around the world.

As CBS2’s Dr. Max Gomez reports, it involves a vaccine for another illness that’s been around for more than a century.

The vaccine is called BCG and it’s actually used to immunize children against tuberculosis. It’s been given nearly four billion times over the past century, mostly in China, Africa and South America, but not that often in the U.S., because TB is less common here. Surprisingly, it may also treat diabetes.

Type one diabetes is at epidemic levels around the globe and increasing rapidly.

It’s an autoimmune disease that attacks the insulin-producing cells in the pancreas, which lets patients’ blood sugar soar. Diabetics have to constantly check their blood sugar to gauge how much insulin they need.

Now, a study just published in NPJ Vaccines has found a completely new approach to controlling type one diabetes – a new use for the BCG tuberculosis vaccine.

“BCG is a hundred-year-old drug, it’s heralded as the safest vaccine in the history of the world. So we’re working with a known drug, a known vaccine, that has impeccable safety,” the principal author Dr. Denise Faustman, from Harvard and Mass General Hospital, said in a YouTube video.

The study found that when adults with longstanding type one diabetes were given two BCG vaccines a month apart, three years later, their diabetes was reversed, their blood sugar stabilized and stayed stable for up to eight years, so far.

The theory for how the vaccine works was thought to be that it re-educated certain white blood cells so they would stop attacking the insulin-producing beta cells in the pancreas. Turns out, it may be doing even more.

“What it seems to show is that the body’s way that it processes glucose is altered when repeated administration of this vaccine,” said Dr. David Lam, of the Icahn School of Medicine at Mount Sinai.

Dr. Faustman is currently running a larger five-year double-blind study where neither the doctors nor diabetics know whether they’re getting the active vaccine. If the results are confirmed, this is a major change in diabetes treatment.

“This is absolutely a big deal for type one diabetes,” Dr. Lam said.

Doctors aren’t ready to call it a cure just yet, but there is a lot of excitement around this – partly because the benefit has lasted for years, and also because the vaccine may stop or slow other autoimmune diseases from rheumatoid arthritis to lupus.