pericarditis;   A 61-year-old female patient received second dose of BNT162B2 (PFIZER-BIONTECH COVID-19 mRNA VACCINE, formulation: Solution for injection, Lot number and Expiration date: Not reported), via unspecified route of administration on an unspecified date as Dose 2, Single for Covid-19 immunization. The patient's medical history included hypertension. The patient's concomitant medication was not reported. On an unknown date, the patient developed low grade fevers, night sweats, chest discomfort and palpitations after four weeks after her second dose of the vaccine. The patient noticed that her symptoms improved when leaning forward. On examination, it was found to have a friction rub. ECG revealed new-onset atrial fibrillation and echocardiography demonstrated a small to moderate circumferential pericardial effusion, echocardiogram: normal RV size and function, small to moderate circumferential pericardial effusion transthoracic echocardiogram, electrocardiogram: new onset atrial fibrillation, transthoracic Echocardiogram: LVEF: 65%; LVIDd: 3.6 cm; Normal RV size and function; Small to moderate circumferential pericardial effusion inflammatory markers were significantly elevated, CRP (C-reactive protein): 23.1 mg/dL (reference range: less than 0.80 mg/dL); ESR (Estimated red blood cell sedimentation rate): 81 mm/hour (reference range: less than 15 mm/hour), Cardiac Biomarkers: Troponin T: undetectable, ventricular internal diameter: 3.6 cm, and viral serologies such as SARS-CoV-2 negative. Cardiac MRI and coronary evaluation was not performed. Based on these clinical features, the patient was diagnosed with pericarditis. The patient was started with on colchicine with improvement in her symptoms. Both patients tested negative for SARS-CoV-2. Long-term follow-up of patients with cardiovascular events following the receipt of mRNA based COVID-19 vaccines is needed. At the time of publication, all patients presented in this case series demonstrated clinical improvement. we report the first case series of patients with myocarditis, stress cardiomyopathy, and pericarditis after receiving the mRNA-based COVID-19 vaccines. While we cannot definitively prove association of the vaccines with these adverse events, we believe reporting these complications may enable further monitoring and investigation. However, it was crucial to emphasize that these findings are rare while SARS-CoV-2 infection was associated with a much higher incidence of cardiovascular complications. The outcome of the event Pericarditis was reported as recovering. ; Sender's Comments: Based on available information, a possible contributory role of BNT162B2 vaccine can not be excluded for the reported event of Pericarditis. 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-202101513854 Same article/drug and different patient/event.