A century-old tuberculosis vaccine reduced insulin use in people with diabetes, new clinical trial results suggest. The catch: Research on this vaccine has divided the diabetes research community for years.

The Bacillus Calmette-Guérin (BCG) vaccine contains a weakened version of the bacterium Mycobacterium bovis, the germ that causes tuberculosis. Inside the body, the vaccine prompts a protective response against the bacterium. It's also approved to treat bladder cancer, acting as an immunotherapy that rouses an attack against tumors.