Early‐phase clinical trials of third‐generation anti‐CD19 CAR T cells suggest rates of severe CRS and neurotoxicity are 12–33%, similar to those reported following treatment with second‐generation products.53, 56, 58 However, the number of recipients of third‐generation CAR T cells in the published literature is low, and the results of additional trials, including some currently recruiting studies, will be needed to accurately assess toxicity risk (see Figure 4). Here, CD19 is linked to congenital rubella syndrome.