NOEL KING, HOST:
Tuberculosis kills more people around the world than any other infectious disease. There is a vaccine for it, but it's not been entirely clear how effective the vaccine is. Researchers have now made a discovery. It involves using the same vaccine but administering it in a different way.
NPR's Pien Huang spoke to the scientists who made the breakthrough.
PIEN HUANG, BYLINE: The tuberculosis vaccine that exists now has been around for almost 100 years. It uses what's basically a form of cow tuberculosis called BCG. And Robert Seder, a researcher with the National Institutes of Health, says it really doesn't work very well.
ROBERT SEDER: It turns out that getting BCG has efficacy against pulmonary tuberculosis really between, say, 0% and 80%.
HUANG: What do you do with that information? It's currently in limited use, mostly given as a vaccine to babies in places where tuberculosis is common. Seder wasn't satisfied with those numbers. He thought it could work better, so he and JoAnne Flynn, an immunologist at the University of Pittsburgh, ran a study where they gave rhesus monkeys super high doses of the same old vaccine as an injection to the bloodstream.
Six months later, they exposed the monkeys to clouds of tuberculosis bacteria. Flynn says when they saw the results...
JOANNE FLYNN: We were stunned (laughter). We were stunned and surprised.
HUANG: They checked it again to make sure it was right.
FLYNN: It turns out that it's true.
HUANG: After three months, 9 out of 10 monkeys that were vaccinated in this new way were protected against the disease. Many showed no signs of the bacteria in their systems at all. The results are published in the journal Nature.
Bill Jacobs, a TB vaccine researcher at Albert Einstein College of Medicine, not affiliated with the study, says the results are impressive.
BILL JACOBS: I've been working on it for 30 years. The entire field has never really seen sterilizing immunity before like what was seen in this animal study.
HUANG: He says the study shows that it's possible to consistently prime immune systems to prevent tuberculosis infections. The researchers are trying to figure out why it worked so well. Flynn says their best guess is that by loading the bloodstream with lots of bacteria, they got key parts of the immune system to recognize it.
FLYNN: And then you have enough T cells that are in the right place - they're in the lungs - in order to fight off the infection.
HUANG: A tuberculosis vaccine that's 90% effective would be a game changer. Every year, 10 million people catch the disease, and 1.7 million people die from it. Still, Jacobs says, this is a ways off from being used in humans. What they gave the monkeys was a high dose of live bacteria, 100 times more than the typical dose, right into the bloodstream. It might not be safe for people, especially those whose immune systems are compromised.
A lot more research will go into figuring out how it works so it can someday lead to a safe vaccine for many humans. Pien Huang, NPR News.
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