Heart failure One side not pumping like it was supposed to; Myocarditis; Pericarditis; This spontaneous case was reported by a consumer and describes the occurrence of CARDIAC FAILURE (Heart failure One side not pumping like it was supposed to), MYOCARDITIS (Myocarditis) and PERICARDITIS (Pericarditis) in a 26-year-old male patient who received mRNA-1273 (Spikevax) for COVID-19 prophylaxis.     The patient had no allergic history and did not undergo a COVID test. Patient had never experienced symptoms like this before receiving the Moderna COVID-19 vaccine.  Patient had no history of myocarditis, pericarditis and COVID-19 infection.  Concomitant products included FLUOXETINE HYDROCHLORIDE (PROZAC) for an unknown indication.   On an unknown date, the patient received second dose of mRNA-1273 (Spikevax) (unknown route) 1 dosage form. On an unknown date, received first dose of mRNA-1273 (Spikevax) (unknown route) dosage was changed to 1 dosage form. In 2021, the patient experienced CARDIAC FAILURE (Heart failure One side not pumping like it was supposed to) (seriousness criteria hospitalization and medically significant), MYOCARDITIS (Myocarditis) (seriousness criteria hospitalization and medically significant) and PERICARDITIS (Pericarditis) (seriousness criteria hospitalization and medically significant). The patient was hospitalized for 4 days due to CARDIAC FAILURE, MYOCARDITIS and PERICARDITIS. At the time of the report, CARDIAC FAILURE (Heart failure One side not pumping like it was supposed to), MYOCARDITIS (Myocarditis) and PERICARDITIS (Pericarditis) had not resolved.            It was reported that patient was in ICU for 4 days. The caller sated that nothing happened after the 1st dose. Reported stated that patient had all the symptoms 2 days after the 2nd dose.  Symptom of chest pain included with Myocarditis and Pericarditis. Symptom of Pallor under Cardiac failure.  Company Comment: This is a Spontaneous case reported by a consumer, concerning a 26-year-old male patient, with no relevant medical history, who experienced the expected and serious (due to hospitalization and medically significant) of Myocarditis and Pericarditis, and the unexpected and serious (due to hospitalization and medically significant) of Cardiac failure, which occurred 2 days after the second dose of mRNA-1273 vaccine. Patient experienced pallor and chest pain. He went to the hospital, and was in intensive care unit (ICU) for 4 days with the diagnosis of myocarditis, pericarditis and heart failure, with one side of his heart not pumping like it was supposed to. At the time of the report, patient continued with severe chest pains. No information disclosed about diagnostic tests performed or treatments received. The benefit-risk relationship of mRNA-1273 is not affected by this report.; Sender's Comments: This is a Spontaneous case reported by a consumer, concerning a 26-year-old male patient, with no relevant medical history, who experienced the expected and serious (due to hospitalization and medically significant) of Myocarditis and Pericarditis, and the unexpected and serious (due to hospitalization and medically significant) of Cardiac failure, which occurred 2 days after the second dose of mRNA-1273 vaccine. Patient experienced pallor and chest pain. He went to the hospital, and was in intensive care unit (ICU) for 4 days with the diagnosis of myocarditis, pericarditis and heart failure, with one side of his heart not pumping like it was supposed to. At the time of the report, patient continued with severe chest pains. No information disclosed about diagnostic tests performed or treatments received. The benefit-risk relationship of mRNA-1273 is not affected by this report.