Seizures; Bood clots; Stuggling to breathe; Struggling to walk; ARDS; Acute hypoxic respiratory failure; Acute exacerbation of heart failure and sepsis; Acute exacerbation of heart failure and sepsis; Cardiac arrest; Blood infection; Fever; This spontaneous case was reported by a patient family member or friend (subsequently medically confirmed) and describes the occurrence of ACUTE RESPIRATORY DISTRESS SYNDROME (ARDS), ACUTE RESPIRATORY FAILURE (Acute hypoxic respiratory failure), SEPSIS (Acute exacerbation of heart failure and sepsis), CARDIAC FAILURE ACUTE (Acute exacerbation of heart failure and sepsis), CARDIAC ARREST (Cardiac arrest), SEIZURE (Seizures), THROMBOSIS (Bood clots), DYSPNOEA (Stuggling to breathe) and GAIT DISTURBANCE (Struggling to walk) in a 53-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.     Concurrent medical conditions included Obesity.   On 16-Apr-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 15-May-2021 at 2:00 PM, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On 15-May-2021, the patient experienced ACUTE RESPIRATORY DISTRESS SYNDROME (ARDS) (seriousness criteria death and medically significant), ACUTE RESPIRATORY FAILURE (Acute hypoxic respiratory failure) (seriousness criteria death and medically significant), DYSPNOEA (Stuggling to breathe) (seriousness criterion hospitalization prolonged) and GAIT DISTURBANCE (Struggling to walk) (seriousness criterion hospitalization prolonged). In May 2021, the patient experienced SEPSIS (Acute exacerbation of heart failure and sepsis) (seriousness criteria death and medically significant), CARDIAC FAILURE ACUTE (Acute exacerbation of heart failure and sepsis) (seriousness criteria death and medically significant), CARDIAC ARREST (Cardiac arrest) (seriousness criteria death and medically significant), INFECTION (Blood infection) and PYREXIA (Fever). On 17-May-2021, the patient experienced SEIZURE (Seizures) (seriousness criteria hospitalization prolonged and medically significant) and THROMBOSIS (Bood clots) (seriousness criteria hospitalization prolonged and medically significant). The patient was hospitalized from 15-May-2021 to 25-May-2021 due to DYSPNOEA, GAIT DISTURBANCE, SEIZURE and THROMBOSIS. The patient died on 25-May-2021. The reported cause of death was Cardiac arrest, Acute hypoxic respiratory failure, ards and acute exacerbation of heart failure and sepsis. It is unknown if an autopsy was performed. At the time of death, SEIZURE (Seizures), THROMBOSIS (Bood clots), DYSPNOEA (Stuggling to breathe), GAIT DISTURBANCE (Struggling to walk), INFECTION (Blood infection) and PYREXIA (Fever) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 15-May-2021, Blood pressure measurement: elevated (High) Twice normal. On 15-May-2021, Glycosylated haemoglobin: elevated (High) High. On 15-May-2021, Oxygen saturation: low (Low) Required intubation and was placed on ventilator.. On 15-May-2021, SARS-CoV-2 antibody test: negative (Negative) 1 negative COVID antibody test. On 15-May-2021, SARS-CoV-2 test: negatie (Negative) 3 negative COVID antigen tests.         No concomitant medications were provided.  It was reported that within few hours after second dose of vaccine patient was struggling to walk and to breathe. The reporter and her husband went to see the patient and took him to an emergency room (ER). In the ER his blood pressure was markedly elevated (twice normal) and his oxygen level was low and by midnight he required intubation and was placed on a ventilator. His HbgA1c was noted to be elevated. Two days after admission (17-May-2021), he developed seizures which the medical team believed to be due to blood clots and he was anti-coagulated. It was determined that he did not have blood clots on his heart valves as the source of the clots. The source of the blood clots was never identified. He later developed fever and was diagnosed with a blood infection and treated with antibiotics. At one point his oxygen requirement on the ventilator went down to 65% but later returned and remained at 100%. He ultimately died on 25-May-2021 and as per copy of his death certificate he had 4 causes of death as cardiac arrest, acute hypoxic respiratory failure, acute respiratory distress syndrome (ARDS) and acute exacerbation of heart failure and sepsis.  Treatment included, anticoagulants, antibiotics, intubation and ventilator.  Very limited information regarding these events has been provided at this time.  Further information has been requested.   This case was linked to MOD-2021-219410 (Patient Link).; Sender's Comments: Very limited information regarding these events has been provided at this time.  Further information has been requested.; Reported Cause(s) of Death: Cardiac arrest; Acute hypoxic respiratory failure; ARDS; Acute exacerbation of heart failure and sepsis