Abstract Text: Despite the undeniable public health benefits of COVID-19 spike-protein vaccines, acute myocarditis have been reported. We describe two cases of recurrent myocarditis following mRNA-Covid-19-vaccine occurring in adolescent males (15 years-old) with no previous history of COVID-19. During the first episode both patients presented with fever and chest pain few days after the second dose of BNT162b2-mRNA-Covid-19 Vaccine. The blood exams showed increased cardiac enzymes, both hsTnT (610 and 450 ng/mL respectively) and NT-proBNP (1000 and 1170 pg/mL respectively). The left ventricular ejection fraction (LVEF) was normal at echocardiogram but cardiac magnetic resonance scanning (CMR) were consistent with myocarditis in both patients (regional hyperintensity on T2-weighted imaging and late gadolinium enhancement). They received supportive treatment with full recovery. The 6-months follow-up evaluation demonstrated good clinical conditions with normal cardiological findings and the CMR showed persistent lesions in left ventricle‘s wall. Few months after the 1st episode (9 and 12 months respectively), both patients presented at ED with fever, chest pain and increased cardiac enzymes. Whereas no decreased LVEF was observed, the CMR showed new focal areas of oedema and stable lesions respectively. HHV7 infection was found in both and supportive treatment along with IGIV was started. Both patients reached full recovery after few days. These case reports warn clinicians on performing a strict follow-up in patients with CMR-confirmed myocarditis following mRNA-based-COVID19 vaccine. More efforts are necessary to depict the underlying mechanisms of myocarditis after SARS-CoV2 vaccination to understand the relapse risk and host-related factors favoring such condition and the long-term sequelae.
