Hypersensitivity myocarditis, or drug-induced myocarditis, is a discrete subtype of eosinophilic myocarditis that can present in 2 forms: the common form, which is neither necrotizing nor fibrotic, with absence of skin rash, malaise, fever, and eosinophilia in 75% of cases, and the second, rarer form, which may present with myocyte necrosis and fibrosis.3 Both forms of hypersensitivity myocarditis are caused by an allergic or hypersensitivity reaction to a variety of drugs and substances, including antibiotics and vaccines. ...according to this classification, one of these boys might have suffered hypersensitivity myocarditis with subepicardial/transmural fibrosis and the other boy may have had hypersensitivity myocarditis with no subepicardial injury. The authors characterized this case as an extremely rare idiosyncratic hypersensitivity reaction.2 Moreover, in another fatal case of post Pfizer-BioNTech mRNA COVID-19 vaccine myocarditis, the autopsy demonstrated dense eosinophilic intracellular strips of myocytes in the Masson trichrome staining, consistent with contraction band necrosis.2 Pfizer-BioNTech mRNA COVID-19 vaccines contain the excipient polyethylene glycol, which could potentially induce hypersensitivity reactions. Mortz CG, Kjaer HF, Rasmussen TH, Rasmussen HM, Garvey LH, Bindslev-Jensen C. Allergy to polyethylene glycol and polysorbates in a patient cohort: diagnostic work-up and decision points for vaccination during the COVID-19 pandemic.