“It’s a very exciting time for the field of cancer vaccines,” says Vinod Balachandran, an oncologist and surgeon-scientist at the Memorial Sloan Kettering Cancer Center. “We have made so much progress in understanding how the immune system recognizes cancers. There are dozens of cancer vaccine candidates under study by researchers around the world.”

The immune system plays a critical role in controlling cancer. Many experts believe that cancers are constantly trying to sprout within us, only to be squelched by the immune system before they become detectable, a process known as immunosurveillance.

“Our bodies are probably rejecting cancers all the time,” says Jay Berzofsky, chief of the National Cancer Institute’s vaccine branch. “The ones we detect and that turn into cancer we need to treat are the ones that have escaped from that immunosurveillance. The tumors do it by learning how to exploit the mechanisms that regulate the immune system.”

The new approaches include developing both preventive and therapeutic vaccines, the latter designed to discern tumor cells from normal cells with the goal of provoking an immune response against them. Researchers also are assembling a collection of immunotherapy drugs that would boost the vaccines’ efficacy.