This spontaneous case was reported by a consumer and describes the occurrence of MYOCARDITIS (myocarditis), DYSPNOEA (shortness of breath), COUGH (cough), BRONCHITIS (bronchitis), PNEUMONIA (pneumonia), HEART RATE DECREASED (heart rate 33), IMPULSE-CONTROL DISORDER (electrical impulses were not working) and CARDIOMEGALY (heart was enlarged) in a 54-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 047A21A and 047A21A) for COVID-19 vaccination.     The patient's past medical history included Coughing (due to sinusitis) and COVID-19 in September 2021. Previously administered products included for COVID-19: Amoxicillin. Past adverse reactions to the above products included No adverse event with Amoxicillin.   On 18-Mar-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 15-Apr-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 02-Dec-2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 13-Dec-2021, the patient experienced DYSPNOEA (shortness of breath) (seriousness criteria hospitalization and medically significant), COUGH (cough) (seriousness criteria hospitalization and medically significant) and PNEUMONIA (pneumonia) (seriousness criteria hospitalization and medically significant). On 16-Dec-2021, the patient experienced MYOCARDITIS (myocarditis) (seriousness criteria hospitalization and medically significant), BRONCHITIS (bronchitis) (seriousness criteria hospitalization and medically significant), HEART RATE DECREASED (heart rate 33) (seriousness criteria hospitalization and medically significant), IMPULSE-CONTROL DISORDER (electrical impulses were not working) (seriousness criteria hospitalization and medically significant) and CARDIOMEGALY (heart was enlarged) (seriousness criteria hospitalization and medically significant). The patient was hospitalized from 16-Dec-2021 to 19-Dec-2021 due to BRONCHITIS, CARDIOMEGALY, COUGH, DYSPNOEA, HEART RATE DECREASED, IMPULSE-CONTROL DISORDER, MYOCARDITIS and PNEUMONIA. The patient was treated with PREDNISONE at an unspecified dose and frequency; Surgery (pacemaker with a defibrillator was placed) for Myocarditis and Surgery (pacemaker with a defibrillator was placed) for Cardiomegaly. At the time of the report, MYOCARDITIS (myocarditis), DYSPNOEA (shortness of breath), COUGH (cough), BRONCHITIS (bronchitis), PNEUMONIA (pneumonia), HEART RATE DECREASED (heart rate 33), IMPULSE-CONTROL DISORDER (electrical impulses were not working) and CARDIOMEGALY (heart was enlarged) had not resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In September 2021, SARS-CoV-1 test: positive (Positive) POSITIVE COVID-19 TEST. On 13-Dec-2021, Chest X-ray: bronchitis and pneumonia (abnormal) Bronchitis and pneumonia. On an unknown date, Electrocardiogram: result not provided Result not provided. On an unknown date, Myocardial necrosis marker: result not provided Result not provided.     The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown) was unknown.       On 13 Dec2021, the patient experienced shortness of breath and cough. He went to see his doctor and X-ray was done which showed bronchitis and pneumonia. He was prescribed with antibiotics and prednisone. His breathing did not improve and on 16 Dec 2021, he was advised to go to the emergency room (ER). At the ER, they found his heart rate to be 33 and that the electrical impulses were not working. His heart was enlarged and he was told that he had myocarditis. The doctors' theory was that this could be due to any of the following: a weird virus, the Moderna Covid-19 vaccine or Covid disease. He was admitted to the hospital on the same day, 16 Dec 2021 and a pacemaker with a defibrillator was placed on him on 17Dec2021. He was discharged from the hospital on 19 Dec 2021.  This case concerns a 54-year-old male patient with no relevant medical history, who experienced the unexpected serious events of Dyspnea, Cough, Pneumonia, Bronchitis, Heart Rate Decreased, Impulse-control Disorder, Cardiomegaly and adverse event of special interest of Myocarditis, all events were medically significant and caused hospitalization of the patient. The events occurred approximately 11-14 days after receiving the third dose of mRNA-1273 Vaccine. The rechallenge was not applicable since no information about the second dose was given. The patient was hospitalized for 3 days and was treated with Prednisone. A pacemaker with defibrillator was also placed. Patient was eventually discharged improved however it was reported that the events had not resolved. No other clinical or treatment details were given. The benefit-risk relationship of mRNA-1273 Vaccine is not affected by this report.   This case was linked to MOD-2021-438261 (Patient Link). Sender's Comments: This case concerns a 54-year-old male patient with no relevant medical history, who experienced the unexpected serious events of Dyspnea, Cough, Pneumonia, Bronchitis, Heart Rate Decreased, Impulse-control Disorder, Cardiomegaly and adverse event of special interest of Myocarditis, all events were medically significant and caused hospitalization of the patient. The events occurred approximately 11-14 days after receiving the third dose of mRNA-1273 Vaccine. The rechallenge was not applicable since no information about the second dose was given. The patient was hospitalized for 3 days and was treated with Prednisone. A pacemaker with defibrillator was also placed. Patient was eventually discharged improved however it was reported that the events had not resolved. No other clinical or treatment details were given. The benefit-risk relationship of mRNA-1273 Vaccine is not affected by this report.