This is a literature report. The reporter reported two reports for same events for 2 patients, this is the first of the report. Recently reported cases of myocarditis and pericarditis after coronavirus disease 2019 (Covid-19) messenger RNA (mRNA) vaccination.1 In recently published reports, diagnosis of myocarditis was made with the use of noninvasive imaging and routine laboratory testing. Here, authors report two cases of histologically confirmed myocarditis after Covid-19 mRNA vaccination. Patient 1, a 45-year-old woman without a viral prodrome, presented with dyspnea and dizziness 10 days after BNT162b2 vaccination (first dose). A nasopharyngeal viral panel was negative for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza A and B, enteroviruses and adenovirus A serum polymerase-chain reaction (PCR) assay and serologic tests showed no evidence of active parvovirus, enterovirus, human immunodeficiency virus, or infection with SARS-CoV-2. At presentation, she had tachycardia ST-segment depression detected on electrocardiography which was most prominent in the lateral leads and a troponin I level of 6.14 ng per milliliter (reference range, 0 to 0.30). A transthoracic echocardiogram showed severe global left ventricular systolic dysfunction (ejection fraction, 15 to 20%) and normal left ventricular dimensions. Right heart catheterization revealed elevated right- and left-sided filling pressures and a cardiac index of 1.66 liters per minute per square meter of body-surface area as measured by the method. Coronary angiography revealed no obstructive coronary artery disease. An endomyocardial biopsy specimen showed an inflammatory infiltrate predominantly composed of T-cells and macrophages, admixed with eosinophils, B cells, and plasma cells received inotropic support, intravenous diuretics methylprednisolone (1 g daily for 3 days), and, eventually, guideline-directed medical therapy for heart failure (lisinopril, spironolactone, and metoprolol succinate). Seven days after presentation, her ejection fraction was 60%, and she was discharged home. In these two adult cases of histologically confirmed, fulminant myocarditis that had developed within 2 weeks after Covid-19 vaccination, a direct causal relationship cannot be definitively established because we did not perform testing for viral genomes or autoantibodies in the tissue specimens. However, no other causes were identified by assay or serologic examination. No follow-up attempts are possible; information about lot/batch number cannot be obtained. No further information is expected. Sender's Comments: Based on temporal association and available information a contributory role of BNT162b2 to the reported fulminant myocarditis cannot be excluded.  Case will be reassessed if additional information is received. The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to regulatory authorities, Ethics Committees, and Investigators, as appropriate. Linked Report(s): PFIZER INC-202101076981 Same reporter/drug/event, different patient.