Introduction: Covid-19 vaccine-associated myocarditis is a novel disease with poorly understood long-term outcomes. 

Case Description: A 17-year-old male presented with nausea, vomiting, and headache three days after receiving the second Pfizer-BioNTech mRNA Covid-19 vaccine. He tested negative for acute Covid-19 infection. Laboratory evaluation revealed elevated troponin and mildly elevated NT-proBNP. Echocardiogram showed normal function. Cardiac MRI showed significant subepicardial delayed gadolinium enhancement. The day of admission, the patient had a 4-beat run of non-sustained ventricular tachycardia (NSVT). Troponin normalized by day 10. Cardiac MRI six months later demonstrated myocardial fibrosis. One month later, the patient developed chest discomfort with exercise. Exercise stress test demonstrated a 3-beat run of NSVT at 230 bpm at peak exercise. 

Discussion: While a rare occurrence, Covid-19 vaccine-associated myocarditis is a known phenomenon. This illness typically occurs in Caucasian males shortly after receiving a Covid-19 mRNA vaccine. The long-term outcomes of Covid-19 vaccine-associated myocarditis have not been reported. An understanding of long-term outcomes can help guide outpatient follow up and determine the need for Holter analysis, axial imaging, and exercise stress test. Current general myocarditis guidelines recommend 24-hour Holter monitoring and exercise stress testing in athletes after 3-6 months and before returning to competition. These recommendations may be useful for patients with Covid-19 vaccine-associated myocarditis.  

Conclusion: Large-scale research into long-term effects of Covid-19 vaccine-associated myocarditis is required. This case describes a patient with Covid-19 vaccine-associated myocarditis who continued to have non-sustained ventricular tachycardia six months after initial diagnosis.