hyperosmolar hyperglycemic syndrome; Diabetic ketoacidosis; Aspiration pneumonia; A lower extremity deep vein thrombosis; fatigue; myalgia; This literature-study case was reported in a literature article and describes the occurrence of HYPERGLYCAEMIC HYPEROSMOLAR NONKETOTIC SYNDROME (hyperosmolar hyperglycemic syndrome), DIABETIC KETOACIDOSIS (Diabetic ketoacidosis), PNEUMONIA ASPIRATION (Aspiration pneumonia) and DEEP VEIN THROMBOSIS (A lower extremity deep vein thrombosis) in an 87-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.        The patient's past medical history included COVID-19 in 2020. Concurrent medical conditions included Type 2 diabetes mellitus, Hypertension, Hyperlipidemia, Ischemic stroke and Congestive heart failure. Concomitant products included METFORMIN for an unknown indication.    On an unknown date, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On an unknown date,  after starting mRNA-1273 (Moderna COVID-19 Vaccine), the patient experienced HYPERGLYCAEMIC HYPEROSMOLAR NONKETOTIC SYNDROME (hyperosmolar hyperglycemic syndrome) (seriousness criteria hospitalization and medically significant), DIABETIC KETOACIDOSIS (Diabetic ketoacidosis) (seriousness criteria hospitalization and medically significant), PNEUMONIA ASPIRATION (Aspiration pneumonia) (seriousness criteria hospitalization and medically significant) and DEEP VEIN THROMBOSIS (A lower extremity deep vein thrombosis) (seriousness criteria hospitalization and medically significant). an unknown date, the patient experienced FATIGUE (fatigue) and MYALGIA (myalgia). The patient was treated with INSULIN GLARGINE (GLARGINE BIOCON) ongoing since an unknown date for Diabetic ketoacidosis, at a dose of 16 unit and ENOXAPARIN for Adverse event, at an unspecified dose and frequency. At the time of the report, HYPERGLYCAEMIC HYPEROSMOLAR NONKETOTIC SYNDROME (hyperosmolar hyperglycemic syndrome), DIABETIC KETOACIDOSIS (Diabetic ketoacidosis), PNEUMONIA ASPIRATION (Aspiration pneumonia), DEEP VEIN THROMBOSIS (A lower extremity deep vein thrombosis), FATIGUE (fatigue) and MYALGIA (myalgia) outcome was unknown. Possible    DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In 2020, SARS-CoV-2 antibody test: positive (Positive) Positive. On an unknown date, Anion gap: 30 meq/l 30 mEq/L. On an unknown date, Blood bicarbonate: 12 meq/l 12 mEq/L. On an unknown date, Blood culture: signs of infection (abnormal) signs of infection. On an unknown date, Blood glucose: 923 mg/dl 923 mg/dL. On an unknown date, Blood ketone body: increased (High) increased to  above 4.0 mmol/. On an unknown date, Blood lactate dehydrogenase: 263 u/l 263 U/L. On an unknown date, Blood lactic acid: 3.6 mmol/l 3.6 mmol/L (RR, <2.5 mmol/L). On an unknown date, Blood osmolarity: 364 mosm/kg 364 mOsm/Kg. On an unknown date, Blood potassium: 6.2meq/l 6.2mEq/L. On an unknown date, Blood pressure measurement: 111/80 111/80. On an unknown date, Blood sodium: 144meq/l 144mEq/L. On an unknown date, Blood urea: 69 mg/dl 69 mg/dL. On an unknown date, Body mass index: 26 26 kg/m2. On an unknown date, Chest X-ray: signs of infection (abnormal) signs of infection. On an unknown date, Computerised tomogram head: negative (Negative) Head computerized tomography (CT) was negative for acute intracranial ischemia or hemorrhage. On an unknown date, Culture urine: signs of infection (abnormal) signs of infection. On an unknown date, Glomerular filtration rate: 18 mg/min 18 mg/min/BSA from a baseline eGFR  above 50 mg/min/BSA. On an unknown date, Haemoglobin: 7.0 7.0 percentage. On an unknown date, Heart rate: 83 83 beats/min. On an unknown date, Oxygen saturation: 100 100% on room air. On an unknown date, Physical examination: abnormal (abnormal) The physical exam revealed a lethargic man, oriented only to self, with dry oral mucous membranes, absent lower extremity edema, lungs clear to auscultation. On an unknown date, Respiratory rate: 18 18/min. On an unknown date, SARS-CoV-2 test: negative (Negative) Negative and negative (Negative) Influenza A and B, and RSV were all negative. On an unknown date, Urine analysis: signs of infection (abnormal) signs of infection. On an unknown date, Vital signs measurement: abnormal (abnormal) afebrile at 36.9 °C. On an unknown date, pH body fluid: 7.2 7.2.     The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown) was unknown.   For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter considered HYPERGLYCAEMIC HYPEROSMOLAR NONKETOTIC SYNDROME (hyperosmolar hyperglycemic syndrome), DIABETIC KETOACIDOSIS (Diabetic ketoacidosis), PNEUMONIA ASPIRATION (Aspiration pneumonia), DEEP VEIN THROMBOSIS (A lower extremity deep vein thrombosis), FATIGUE (fatigue) and MYALGIA (myalgia) to be possibly related.    Without evidence of another precipitant and symptom onset within 48 hours of vaccination, the HHS and DKA were potentially triggered in the setting of COVID-19 vaccination. There was no prior history of DKA or HHS. Intravenous normal saline hydration and a continuous insulin infusion were immediately initiated and were continued until both the anion gap and serum osmolality normalized, at which point he was transitioned to a subcutaneous basal-bolus insulin regimen. The hospital course was unfortunately complicated by aspiration pneumonia and a lower extremity deep vein thrombosis for which the patient was treated with antibiotics and enoxaparin, respectively. The initial AKI improved to a GFR of 59 mg/min/BSA with return of mental status back to patient's baseline; he was discharged home on glargine 16 units once daily and metformin 500 mg twice daily. On outpatient follow-up, the regimen has since been further simplified to only metformin  This literature case concerns an 87-year-old, male patient with a history of Type 2 diabetes mellitus and previous COVID-19 disease, who experienced the unexpected serious events of hyperosmolar hyperglycemic syndrome and Diabetic ketoacidosis, which led to hospitalization, which was complicated by unexpected serious events of Pneumonia aspiration and Deep vein thrombosis. The initial events occurred approximately 10 days after the first dose of mRNA-1273 vaccine. The rechallenge was unknown since the events happened after the first dose and no information on additional dosing is available. The medical history of Type 2 diabetes mellitus and previous COVID-19 disease remains as confounders. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report. Case was assessed as serious due to important medical event and hospitalization.   This case was linked to MOD-2021-394116 (Patient Link).   Most recent FOLLOW-UP information incorporated above includes: On 24-Nov-2021: Follow up received by safety 25-Sep-2021 included an Email and contains new information: medical history,  patient details, lab details and events are Added.; Sender's Comments: This literature case concerns an 87-year-old, male patient with a history of Type 2 diabetes mellitus and previous COVID-19 disease, who experienced the unexpected serious events of hyperosmolar hyperglycemic syndrome and Diabetic ketoacidosis, which led to hospitalization, which was complicated by unexpected serious events of Pneumonia aspiration and Deep vein thrombosis. The initial events occurred approximately 10 days after the first dose of mRNA-1273 vaccine. The rechallenge was unknown since the events happened after the first dose and no information on additional dosing is available. The medical history of Type 2 diabetes mellitus and previous COVID-19 disease remains as confounders. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report. Case was assessed as serious due to important medical event and hospitalization.