Provided herein, in one aspect, is a method of preventing or delaying the onset of clinical type 1 diabetes (T1D), comprising: providing a non-diabetic subject who is at risk for T1D; determining that the non-diabetic subject (1) is substantially free of antibodies against zinc transporter 8 (ZnT8), (2) is HLA-DR4+, and/or (3) is not HLA-DR3+; and administering a prophylactically effective amount of an anti-CD3 antibody to the non-diabetic subject.