This randomized phase II trial studies how well glycosylated recombinant human interleukin-7 (CYT107) after vaccine therapy works in treating patients with castration-resistant prostate cancer that has spread to other areas of the body or has not responded to at least one type of treatment. Biological therapies, such as glycosylated recombinant human interleukin-7, may stimulate the immune system in different ways and stop tumor cells from growing. Vaccines made from white blood cells mixed with tumor proteins may help the body build an effective immune response to kill tumor cells. It is not yet known whether glycosylated recombinant human interleukin-7 works better with or without vaccine therapy in treating prostate cancer.