Eosinophilic-lymphocytic myocarditis after smallpox vaccination.

Smallpox is an eradicated viral disease that has re-emerged as a potential bioterrorism threat. Smallpox vaccination was historically the most effective defence measure against wild smallpox virus. The risk of myopericarditis after vaccination might limit this option. We report a case of biopsy-proven eosinophilic-lymphocytic myocarditis diagnosed in vivo with histological evidence for eosinophil-mediated cardiac myocyte necrosis shortly after smallpox vaccination. Furthermore, we report a beneficial haemodynamic response to high-dose corticosteroids. A better understanding of the aberrant immune mechanism of myocyte injury after smallpox vaccination might improve the risk/benefit assessment for people considering smallpox vaccination and better smallpox vaccines in the future.