Myocarditis; This literature-non-study case was reported in a literature article and describes the occurrence of MYOCARDITIS (Myocarditis) in a 26-year-old male patient who received mRNA-1273 (Spikevax) for COVID-19 prophylaxis.        No Medical History information was reported.    On an unknown date, the patient received first dose of mRNA-1273 (Spikevax) (unknown route) 1 dosage form. On an unknown date, the patient experienced MYOCARDITIS (Myocarditis) (seriousness criteria hospitalization and medically significant). The patient was hospitalized for 1 day due to MYOCARDITIS. At the time of the report, MYOCARDITIS (Myocarditis) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Angiocardiogram: No evidence of coronary disease. On an unknown date, Blood creatinine: 1.03 mg/dl. On an unknown date, Blood pressure systolic: 102 mmHg. On an unknown date, Body surface area: 2 square metre. On an unknown date, C-reactive protein (0-10 milligram per litre): 9.6 milligram per litre. On an unknown date, Echocardiogram: LVEF (Left ventricular ejection fraction) 65%,  no regional  WMA (wall-motion abnormality).. On an unknown date, Electrocardiogram: STE(ST elevation) of inferior and lateral leads, incomplete RBBB(Right bundle branch block). On an unknown date, Fibrin D dimer (Unknown-500 ng/mL): 1330 ng/mL. On an unknown date, Heart rate: 65 bpm. On an unknown date, Magnetic resonance imaging heart: LVEF 51%, LGE (Late gadolinium enhancement) identified focal punctate lesions in the lateral wall; STIR (short T2 inversion recovery) imaging identified myocardial edema in the same area.  4-chamber (4C) -short T2 inversion recovery (STIR) imaging specifically identifies increased interstitial space from either myocyte loss or edema, showing increased signal in the lateral left ventricular (LV) wall suggesting acute myocardial edema. This is less obvious on follow-up imaging conducted 57 days later.. On an unknown date, Nasopharyngeal swab: Negative. On an unknown date, Platelet count (150-400 microliter): 278 microliter. On an unknown date, Red blood cell sedimentation rate (0-10 mm/hr): 8 mm/hr. On an unknown date, Troponin I: 44.50 ng/mL.     The action taken with mRNA-1273 (Spikevax) (Unknown) was unknown.   For mRNA-1273 (Spikevax) (Unknown), the reporter considered MYOCARDITIS (Myocarditis) to be related.    Concomitant medications were not reported.  Patient had symptoms of chest pain radiating to left arm.  Arrhythmias during hospitalization was reported as none. Patient had areas of focal punctate LGE on the initial study that were diminished but still present >1 month later.  Author investigated 7 COVID-19 and 6 post-mRNA vaccination patients with myocardial injury and found nearly identical alterations in gene expression that would predispose to inflammation, coagulopathy, and myocardial dysfunction. In summary, it appears that histopathologic findings in myocardial injury associated with COVID-19 or mRNA vaccine can be due to causes other than myocarditis.      This case was linked to US-MODERNATX, INC.-MOD-2022-670442, US-MODERNATX, INC.-MOD-2022-670443, US-MODERNATX, INC.-MOD-2022-670444, US-MODERNATX, INC.-MOD-2022-668401 (Linked Report).  Company comment: This literature non-study case concerns a 26-year-old male patient, with no cardiac history or other medical history reported, who experienced the expected and serious (due to hospitalization and medically significant) AESI of Myocarditis, which occurred 4 days after the first dose of mRNA-1273 vaccine. Patient experienced chest pain radiating to left arm. He was hospitalized for 1 day and several diagnostic studies were performed. Lab data showed fibrin D-dimer high (1330 ng/ml, with a normal range of unknown-500 ng/ml), troponin I of 44.5 ng/ml, normal red blood cell sedimentation and C-reactive protein, among others. SARS-CoV-2 test was negative. Electrocardiogram revealed ST elevation of inferior and lateral leads and incomplete right bundle branch block. Echocardiogram showed left ventricular ejection fraction (LVEF) of 65%, with no regional wall-motion abnormality. Cardiac magnetic resonance (CMR) was consistent with myocarditis, with a LVEF of 51%, late gadolinium enhancement (LGE) that identified focal punctate lesions in lateral wall, as well as myocardial edema in the same area. Angiocardiogram showed no evidence of coronary disease. Corticosteroids were not administered, and no information about other treatments was disclosed. Follow-up CMR showed focal punctate LGE diminished but still present more than 1 month later. The benefit-risk relationship of mRNA-1273 is not affected by this report.; Sender's Comments: This literature non-study case concerns a 26-year-old male patient, with no cardiac history or other medical history reported, who experienced the expected and serious (due to hospitalization and medically significant) AESI of Myocarditis, which occurred 4 days after the first dose of mRNA-1273 vaccine. Patient experienced chest pain radiating to left arm. He was hospitalized for 1 day and several diagnostic studies were performed. Lab data showed fibrin D-dimer high (1330 ng/ml, with a normal range of unknown-500 ng/ml), troponin I of 44.5 ng/ml, normal red blood cell sedimentation and C-reactive protein, among others. SARS-CoV-2 test was negative. Electrocardiogram revealed ST elevation of inferior and lateral leads and incomplete right bundle branch block. Echocardiogram showed left ventricular ejection fraction (LVEF) of 65%, with no regional wall-motion abnormality. Cardiac magnetic resonance (CMR) was consistent with myocarditis, with a LVEF of 51%, late gadolinium enhancement (LGE) that identified focal punctate lesions in lateral wall, as well as myocardial edema in the same area. Angiocardiogram showed no evidence of coronary disease. Corticosteroids were not administered, and no information about other treatments was disclosed. Follow-up CMR showed focal punctate LGE diminished but still present more than 1 month later. The benefit-risk relationship of mRNA-1273 is not affected by this report. US-MODERNATX, INC.-MOD-2022-670444:21-YO-Male US-MODERNATX, INC.-MOD-2022-670442:55-YO-Female US-MODERNATX, INC.-MOD-2022-670443:34-YO-Male US-MODERNATX, INC.-MOD-2022-668401:23-YO-Female