For example, PROSTVAC was a promising viral cancer vaccine, composed of a vaccinia priming vector and a fowlpox boosting vector carrying transgenes for human prostate-specific antigen (PSA) along with three costimulatory molecules (CD80, CD58, and CD54), but it failed to benefit the patients in a phase III study (Gulley et al., 2019; Zhao et al., 2019). The gene discussed is KLK3; the disease is cancer.