Severe Diabetic Ketoacidosis; Leucocytosis; Tachypneic; Tachycardic; Severe Nausea; This literature-non-study case was reported in a literature article and describes the occurrence of DIABETIC KETOACIDOSIS (Severe Diabetic Ketoacidosis) in a 24-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.    Concurrent medical conditions included Type 1 diabetes mellitus and Obesity.    On an unknown date, the patient received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On an unknown date, the patient experienced DIABETIC KETOACIDOSIS (Severe Diabetic Ketoacidosis) (seriousness criteria hospitalization and medically significant), LEUKOCYTOSIS (Leucocytosis), TACHYPNOEA (Tachypneic), TACHYCARDIA (Tachycardic) and NAUSEA (Severe Nausea). The patient was treated with INSULIN for Diabetic ketoacidosis, at an unspecified dose and frequency. At the time of the report, DIABETIC KETOACIDOSIS (Severe Diabetic Ketoacidosis) and LEUKOCYTOSIS (Leucocytosis) had resolved and TACHYPNOEA (Tachypneic), TACHYCARDIA (Tachycardic) and NAUSEA (Severe Nausea) outcome was unknown. Possible    DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Anion gap: 27 anion gap 27. On an unknown date, Blood bicarbonate: 14 meq/l bicarbonate 14 meq/L. On an unknown date, Blood glucose: 500 mg/dl (High) Blood glucose rose above 500 mg/dL and 505 mg/dl (High) serum glucose 505 mg/dL. On an unknown date, Computerised tomogram: non-specific discoid atelectasis of the lower lobe computed tomography of the lungs demonstrated non-specific discoid atelectasis of the lower lobes. On an unknown date, Glycosylated haemoglobin: 12.0% (High) hemoglobin A1c 12.0%.. On an unknown date, Neutrophil count: 84% neutrophils 84%. On an unknown date, SARS-CoV-2 antibody test: negative (Negative) Negative COVID-19. On an unknown date, Urine ketone body: large urine ketones large urine ketones. On an unknown date, White blood cell count: 16.56 k/mm3 (High) White cell count was elevated (16.56 K/mm3).     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter considered DIABETIC KETOACIDOSIS (Severe Diabetic Ketoacidosis), LEUKOCYTOSIS (Leucocytosis), TACHYPNOEA (Tachypneic), TACHYCARDIA (Tachycardic) and NAUSEA (Severe Nausea) to be possibly related.    This patient developed severe nausea 15 hours after vaccination, and blood glucose rose above 500 mg/dL. Despite multiple boluses of insulin via her insulin pump and changing the insulin pump delivery site, the patient remained severely hyperglycemic.  The patient's home insulin total daily dose was 45 units/d. However, during the hospitalization, the patient was initially profoundly insulin resistant, requiring more than 220 units of intravenous regular insulin in the first 24 hours. On the third hospital day, insulin infusion requirements decreased to 1 unit/h, the diabetic ketoacidosis and leukocytosis resolved, and the patient was transitioned back to her subcutaneous insulin pump.  Company Comment: This is a literature review case that concerns a 24 year old female with a history of Type 1 Diabetes and Obesity who experienced the unexpected event of Diabetic Ketoacidosis requiring hospitalization along with other non-serious events. The events occurred 15 hours after the second dose of Moderna COVID-19 vaccine. Rechallenge is not applicable as this was the second dose and no information is available for the first dose. The medical history of insulin dependent Type 1 Diabetes, uncontrolled as evidenced by a Hb A1c of 12%, and Obesity which can cause the events remain confounders. Benefit-risk relationship of Moderna COVID-19 vaccine is not affected by this report.   Most recent FOLLOW-UP information incorporated above includes: On 21-Sep-2021: Follow up received by safety on 22-Sep-2021 has Email with FTA received from team.; Sender's Comments: This is a literature review case that concerns a 24 year old female with a history of Type 1 Diabetes and Obesity who experienced the unexpected event of Diabetic Ketoacidosis requiring hospitalization along with other non-serious events. The events occurred 15 hours after the second dose of Moderna COVID-19 vaccine. Rechallenge is not applicable as this was the second dose and no information is available for the first dose. The medical history of insulin dependent Type 1 Diabetes, uncontrolled as evidenced by a Hb A1c of 12%, and Obesity which can cause the events remain confounders. Benefit-risk relationship of Moderna COVID-19 vaccine is not affected by this report.