This is an observational, prospective cohort study designed to evaluate the outcomes after teplizumab treatment in participants with Stage 2 Type 1 Diabetes (T1D) for delaying the onset of Stage 3 T1D. The study will monitor participants receiving teplizumab as part of routine clinical care across multiple sites. Additionally, patient-reported outcomes (PROs) will be evaluated to further assess the treatment's impact on participant's quality of life including emotional and psychosocial aspects associated with T1D. This approach will provide a more comprehensive understanding of how the treatment performs over time and across diverse patient populations, providing valuable insights into the sustained effects of teplizumab and offering a real world picture of its impact on the long-term management of T1D.