CD19 and congenital rubella syndrome: Peak ferritins (defined as the highest value in the first month after CD19‐targeted CAR‐T cells infusion) were very high in all patients (median 2717 ng/mL, range 157.5 – 998997 ng/mL) regardless of grade (p < 0.0001), but there was no significant difference between mild (grades 1–3) and severe CRS(grades 4–5) (p = 0.0559).