evidence: There is evidence that the COVID-19 mRNA vaccine can cause myocarditis, particularly in cases of the previous exposure. With most patients presenting after both doses of the vaccine, or after the first dose with prior SARS-CoV-2 infection, there may be a possibility of a hypersensitivity reaction occurring after the previous exposure [61, 64]. This reaction may be a delayed-type hypersensitivity reaction due to the two- to three-day period between vaccine administration and onset of symptoms seen in most patients [56, 64]. The first vaccine dose could act to sensitize the immune system, while the second dose causes the activation of the effector phase of the immune system [64]. Activated immune cells may migrate to the myocardium leading to release of cytokines into the myocardium. This process can stimulate further immune cells to enter the myocardium, leading to inflammation and the patient may present with myocarditis.