Myocarditis; This is a literature report for the following literature source(s):   A 16-year-old male patient received BNT162b2 (BNT162B2), as dose 1, single (Batch/Lot number: unknown) for covid-19 immunisation. The patient's relevant medical history included: "mild COVID-19 infection" (unspecified if ongoing), notes: months before presentation. The patient's concomitant medications were not reported. The following information was reported: MYOCARDITIS (hospitalization, medically significant, life threatening), outcome "recovered". The patient underwent the following laboratory tests and procedures: Blood immunoglobulin G (normal high range 0.8): 8.2, notes: intermediate 0.8-1, positive greater than 1; C-reactive protein (0.1-1.7): 55 mg/l, notes: Peak; C-reactive protein (normal high range 8.1): 60 mg/l, notes: High-sensitivity; Initial; Echocardiogram: showed normal biventricular, notes: size/function and proximal coronary arteries; Lymphocyte count: 27 %; SARS-CoV-2 test: Negative; Troponin (normal high range 0.05): 13.3 ng/ml, notes: Initial; 13.3 ng/ml, notes: Peak; White blood cell count: 7.4 x10 9/l. Therapeutic measures were taken as a result of myocarditis.  Clinical information: As of June 21, 2021, approximately 318 million COVID-19 vaccine doses have been administered in this demographic area. [1] The Pfizer-BioNTech COVID-19 mRNA vaccine received Emergency Use Authorization from Drug Administration for individuals =16 years in December 2020 and those 1215 years in May 2021.[2] While the Pfizer-BioNTech COVID-19 vaccine trials included over 43,000 participants =16 years in Phase 2/3, the number of participants in the younger age groups was limited. According to the Pfizer-BioNTech COVID-19 mRNA Vaccine Fact Sheet, Phase 2/3 included 138 and 145 adolescents 16 and 17 years of age in the vaccine and placebo groups, respectively. There were 2260 participants aged 1215 years: 1131 and 1129 in the vaccine and placebo groups, respectively.[2] It is possible that rare adverse events could manifest when administered to a larger population. We report three healthy male adolescents diagnosed with myocarditis following Pfizer-BioNTech COVID-19 vaccination, confirmed on cardiac magnetic resonance imaging (CMR). A 16-year-old previously healthy male presented to the ED with chest pain 3 days after receiving his first dose of Pfizer-BioNTech COVID-19 vaccine. He had a subjective fever 1 day after vaccination. The following day, he developed sharp left-sided chest pain, exacerbated by deep breathing, with radiation to the left upper extremity. There were no preceding URI or GI symptoms. Notably, he had a mild COVID-19 infection 5 months before presentation. He had a normal ECG and troponin-I of 13.3 (normal <0.05 ng/ml) on presentation [Table 1]. An echocardiogram showed normal biventricular size/function and proximal coronary arteries. The patient received IVIG (2 g/kg) and was started on steroids and aspirin. CMR was consistent with myocarditis: hyperemia at the LV base and mid-LV, and a small focus of LGE at the mid-LV inferolateral segment. As his symptoms and troponin improved, he was discharged with exercise restrictions, steroids, and aspirin after 3 days of hospitalization. At the 2-week follow-up, labs, ECG, and echocardiogram were normal. Aspirin was discontinued and he was placed on tapering dose of steroid. Conclusion COVID-19 vaccine-related myocarditis is an emerging entity that must be closely examined and reported to the Vaccine Adverse Event Reporting System. All published cases to date have had good clinical outcomes in the short term, and it is vitally important to collect long-term data in this population. It is crucial to remember this entity can mimic acute coronary syndrome, to avoid unnecessary procedures for adolescents in whom ischemic coronary disease is exceedingly rare. CMR is the gold standard noninvasive test that can help establish the diagnosis of myocarditis. Larger studies are needed to further delineate the association between the Pfizer-BioNTech COVID-19 vaccine and myocarditis. We recommend following Centers for Disease Control guidelines and updates.; Sender's Comments: As there is limited information in the case provided, the causal association between the event and the suspect drug cannot be excluded. The case will be reassessed once new information is available.  The impact of this report on the benefit-risk profile of the Pfizer product and on the conduct of the study 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) : US-PFIZER INC-PV202300023917 Same article/patient/drug different event; US-PFIZER INC-202300056978 Same article/patient/drug different event.