Blocked main artery going to the heart after 2nd shot/Blood clot in his heart  after 2nd shot; Myocarditis after 2nd shot/Inflammation of the heart after 2nd shot; Fever 101 F  after 2nd shot; This spontaneous case was reported by a consumer and describes the occurrence of ATRIAL THROMBOSIS (Blocked main artery going to the heart after 2nd shot/Blood clot in his heart  after 2nd shot) and MYOCARDITIS (Myocarditis after 2nd shot/Inflammation of the heart after 2nd shot) in a 73-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 032L20A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Concurrent medical conditions included Allergy.   On 29-Jan-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 26-Feb-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 26-Feb-2021, the patient experienced PYREXIA (Fever 101 F  after 2nd shot). On 10-Mar-2021, the patient experienced ATRIAL THROMBOSIS (Blocked main artery going to the heart after 2nd shot/Blood clot in his heart  after 2nd shot) (seriousness criteria hospitalization, medically significant and life threatening) and MYOCARDITIS (Myocarditis after 2nd shot/Inflammation of the heart after 2nd shot) (seriousness criteria hospitalization, medically significant and life threatening). The patient was hospitalized on 10-Mar-2021 due to ATRIAL THROMBOSIS and MYOCARDITIS. On 05-Mar-2021, PYREXIA (Fever 101 F  after 2nd shot) had resolved. At the time of the report, ATRIAL THROMBOSIS (Blocked main artery going to the heart after 2nd shot/Blood clot in his heart  after 2nd shot) and MYOCARDITIS (Myocarditis after 2nd shot/Inflammation of the heart after 2nd shot) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 26-Feb-2021, Body temperature: 101 f (High) 101 F.         No concomitant medications were provided. No treatment information was provided. Right away after the 2nd shot,  he had a Fever (101 Fahrenheit). Twelve days later he had to visit the emergency room. He was diagnosed with a blood clot in his heart which blocked the main artery going to the heart. Due to the inflammation of the heart he had Myocarditis. He states that at doctor's office he administered both shots. The doctor told him that the second shot probably caused the Myocarditis. He did not had a history of Myocarditis and no history of COVID-19 Disease. He stated that the doctor did not recommend to get a booster shot at all. He was concerned that his immunity was waning.  Company comment: This case concerns a 73 -year- old male patient, with no medical history reported, who experienced serious unexpected AESI of atrial thrombosis and serious expected AESI of myocarditis after second dose of mRNA-1273. The events occurred 13 days after vaccination. The re-challenge is not applicable since event outcome were unknown and occurred after second dose. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.; Sender's Comments: This case concerns a 73 -year- old male patient, with no medical history reported, who experienced serious unexpected AESI of atrial thrombosis and serious expected AESI of myocarditis after second dose of mRNA-1273. The events occurred 13 days after vaccination. The re-challenge is not applicable since event outcome were unknown and occurred after second dose. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.