In this study, despite the high rate of MRD‐negative CR/CRi (8/10, 80%) demonstrates that infusion of our CD19 CAR‐T product is an effective salvage therapy for pediatric and young adults with relapsed/refractory B‐ALL, there was a significant risk of relapse (4/8, 50%) during 3 to 6 months after CAR‐T infusion. Here, CD19 is linked to acute lymphoblastic leukemia.