The world’s most advanced tuberculosis vaccine failed to protect babies against the infectious disease, according to a new study in South Africa.

The vaccine, MVA85A, was designed to improve protection from the only existing tuberculosis vaccine, BCG, which is routinely given to newborns.

Though the new vaccine appeared safe, scientists found no proof it prevented tuberculosis, an airborne disease that kills more than 1 million people worldwide every year.

Previous tests of the vaccine in adults had been promising and researchers said the trial provided useful data to inform future studies. There are a dozen other TB vaccines currently being tested.