The new vaccine, MVA85A, was developed to be an improvement over what was previously the only existing TB vaccine, BCG, which is routinely given to newborns. While the new vaccine appeared safe, scientists found no evidence that proved it was effective in preventing tuberculosis – and airborne disease that kills more than 1 million people worldwide every year.
Earlier tests of the MVA5A vaccine in adults had been promising, with researchers saying they provided useful data for future studies, such as a dozen other TB vaccines that are currently being tested.
The results of the new study, which found the MVA85A vaccine failed to protect babies, has therefore left some discouraged.
"It's pretty disappointing," said Dr. Jennifer Cohn, a medical coordinator at Doctors Without Borders, told The Associated Press. "Infants are at really high risk of TB but this doesn't seem to offer them any protection."
The new TB vaccine was developed at Oxford University, with researchers testing nearly 2,800 babies in South Africa who had already received a BCG shot between 2009 and 2011. Around half of the infants were given the new TB vaccine, and the other half were given a placebo. They were then followed for up to three years.
In the group that received the new vaccine, 32 got TB. In the group that received a placebo, 39 got TB; which equates to an approximate 17 percent efficacy rate for the vaccine.
"There is much that we and others can learn from the study and the data it has produced," said study author Helen McShane of the University of Oxford in a statement. She and her colleagues are continuing to analyze samples from the trial to learn more about how humans become infected with tuberculosis bacteria.
McShane and co-authors of the study wrote that the vaccine could potentially protect adolescents or adults against TB since their immune systems work differently from those of infants. The vaccine is also currently being tested in people with HIV.