Although its sufficient efficacy was demonstrated, a novel oral WT1 protein vaccine is required for cancer patients (especially, pediatric patients), which is devoid of pain- and scarring-causing adjuvant MontanideTM and instead uses Bifidobacterium longum (B. longum)—a normal intestinal bacterium that is a probiotic with established safety acting as an adjuvant [10] and has low human leukocyte antigen (HLA) restriction because of protein nature [11]. The gene discussed is WT1; the disease is cancer.