A clinical trial shows that adding a personalized mRNA vaccine to standard melanoma treatment cut the risk of death or cancer returning by 42 percent compared to standard treatment alone. Melanoma is the deadliest form of skin cancer. It starts in pigment-producing skin cells and is likely to return or spread to other organs. The new mRNA vaccine trains the immune system to find and destroy mutations in remaining cancer cells. Researchers are also trying personalized mRNA vaccines to treat pancreatic cancer.