An experimental vaccine to prevent progression of Type 1 diabetes failed at the second step of the three-phase trial process, doctors said.

The vaccine sought to protect insulin-producing beta cells in the pancreas from the body’s immune system.

Its formula is based on an enzyme called glutamic acid decarboxylase (GAD), which the over-sensitised immune system targets – and in doing so destroys the precious beta cells.

The idea was that by vaccinating patients with GAD, this would teach the immune system’s T cells to tolerate the enzyme.

The trial was carried out on 145 patients aged three to 45 years living in the United States and Canada who had been diagnosed with Type 1 diabetes within the previous three months.

The volunteers were given either the vaccine; the vaccine plus a standard immune-system booster; or just the booster alone.

Patients in all three groups experienced similar progression in the disease, with no difference among them in side effects.

The paper, led by Jay Skyler of the University of Miami Miller School of Medicine, was presented at a conference of the American Diabetes Association in San Diego, California.