Narrator: This is Science Today. About 20 million Americans suffer from asthma, a disease that causes airways of the lungs to tighten. Asthma medications control the symptoms, but scientists have developed an asthma vaccine, which in animal studies, has stopped the disease. Cell biologist Charles Plopper of the University of California, Davis says the vaccine works by modifying the immune system.

Plopper: There's a whole set of receptors that are on the surfaces of cells that respond to various types of agents. This is DNA that comes from a bacterium – it's a bacterial type of DNA form and there is one receptor that it responds to specifically. And that generates the type of response that would be to an infection – not an allergic response, but an infectious response.

Narrator: This causes the body to recognize the bacterial DNA as a foreign substance, so the immune system is activated to fight off what appears to be an infection. The vaccine also reversed asthma-induced lung damage. Tests in humans are now being conducted. For Science Today, I'm Larissa Branin.