Extended Follow-up of Type 1 Diabetes Immunotherapy Trial Participants Suggests Benign Side Effect Profile

OBJECTIVE: Long-term side effect surveillance after immunotherapy clinical trial participation in individuals with or at risk of type 1 diabetes is needed. RESEARCH DESIGN AND METHODS: Participants from 14 randomized controlled trials (47%) joined the Long-term Investigative Follow-up in Type 1 Diabetes TrialNet or Immune Tolerance Network Type 1 Diabetes Extension Study, and 98% answered at least one health-related outcomes question. RESULTS: Participants were observed for a median of 1.78 (interquartile range 0.89-4.04) years after original trial completion and, in some, up to 18 years. There were no differences in the frequency of self-reported health outcomes, including moderate to severe hypoglycemia events, hospitalizations, serious infections (including COVID-19 infection), new allergic reactions, autoimmune disease, and cancer incidence, between those receiving active and placebo therapy (n = 209-473 responses per question; P > 0.05 for all). CONCLUSIONS: We observed no differences in self-reported health outcomes between those who received active immunotherapy versus placebo. Continued long-term follow-up of immunotherapy trial participants is essential.