CD19 and infection: Based on previous research on infections after CAR-T therapy, we collected relevant risk factors of patients with B cell malignancies (B-ALL and NHL) who received CD19 CAR-T therapy at Tianjin First Central Hospital (ChiCTR-ONC-16008911) to identify and evaluate the risk factors associated with viral infection after CD19 CAR-T therapy, and construct prediction models and perform clinical decision curve analyses to assess the accuracy and clinical value of the models.