Incidence of infection was higher in patients who received a higher CAR–T-cell dose, and high CAR–T-cell doses are associated with an increased risk of CRS and neurotoxicity   Infections in adult patients with relapsed B-ALL are common after CD19 CAR T-cell therapy. Understanding the infectious complications that are temporally coincident with CD19 CAR T-cell therapy is critical for developing effective prophylactic and other supportive care measures to improve clinical outcomes. Here, CD19 is linked to infection.