Narrator: This is Science Today. In studying the incidence of childhood leukemia, researchers aim to first understand the genetic events that lead to this disease. Joseph Wiemels, a research epidemiologist at the University of California, San Francisco says from there, researchers can then devise preventative measures.

Wiemels: Preventive measures may just be recommendations or they may be a cancer vaccine. It turns out that stimulating your immune system early in life actually prevents childhood leukemia. Normal vaccines given at a normal time is actually preventative for leukemia.

Narrator: Having older siblings also gives a child less risk of leukemia, because infections are passed down to the child from the older children at a very early age.

Wiemels: There are several pieces of evidence like that coming together, which show that it's actually early stimulation of the immune system which then modulates these cells that eventually become leukemic. They become modulated and suppressed at an early age in life if you get the proper stimulation of your immune system.

Narrator: For Science Today, I'm Larissa Branin.