New-onset Type 1 Diabetes after COVID-19 mRNA Vaccination.

During the ongoing coronavirus disease 2019 (COVID-19) pandemic, it is critical to ensure the safety of COVID-19 vaccines. We herein report a 51-year-old Japanese woman who developed acute-onset type 1 diabetes with diabetic ketoacidosis six weeks after receiving the first dose of a COVID-19 messenger ribonucleic acid (mRNA) vaccine. Laboratory tests indicated exhaustion of endogenous insulin secretion, a positive result for insulin autoantibody, and latent thyroid autoimmunity. Human leukocyte antigen typing was homozygous for DRB1*09:01-DQB1*03:03 haplotypes. This case suggests that COVID-19 vaccination can induce type 1 diabetes in some individuals with a genetic predisposition.