We report the first cases of tissue-proven eosinophilic myocarditis after single vaccine administration of conjugate meningococcal C and hepatitis B vaccine, respectively. The nature of histopathologic findings strongly supports hypersensitivity reaction and negates viral etiology, which is typically characterized by a lymphocytic infiltrate. Both episodes resolved with corticosteroid therapy.
To enhance discussion of our cases, we performed a systematic review of the literature on postimmunization myocarditis or pericarditis, and identified 37 publications, reporting 269 cases during the search period (1966–2007). Time of onset of cardiac symptoms in all patients ranged from 1 to 30 days postimmunization.