CD22 and precursor B-cell acute lymphoblastic leukemia: Here, we report a patient who developed possible CMV-pneumonia three months after anti-CD19 and anti-CD22 CAR-T cell therapy for relapsed B-ALL, contributing to the understanding of severe side-effects mediated by virus infection or reactivation in patients receiving CAR-T cell infusion.<h4>Case presentation</h4>A 21-year old male patient with relapsed B-ALL received anti-CD19/22 CAR-T cell therapy, and achieved complete remission 2 weeks after the infusion.