Fig. 1.

Examples of different histologic patterns of vaccine-associated myocarditis. (A) Lymphocytic myocarditis, the most common pattern reported in COVID-19 vaccination–associated myocarditis, is characterized by a dense mononuclear infiltrate and associated myocyte damage. (B) Healing myocarditis is more typically characterized by a loose and more mixed inflammatory infiltrate and with underlying damage already entering stages of repair (matrix formation). (C) Eosinophilic myocarditis, the pattern typically associated with other vaccinations, is characterized by a patchy infiltrate of eosinophils with relatively little cardiomyocyte damage. All images are hematoxylin and eosin (H&E)-stained slides, digital image capture (Leica DM2500 microscope, 200x original magnification with 10x Plan ocular and 20x FluorTar objective, OMAX 18MP camera, Toupview software, post-processing in GNU Image Manipulator Program 2.0); scale bar as indicated (100 μm).