Post-vaccination myocarditis could be causally linked to the vaccine affecting vascular muscle cells in the heart, leading to the production of bacterial proteins not typically found in these cells.

The vaccine's mRNA, encapsulated in lipid nanoparticles, might preferentially enter vascular muscle cells, where it is translated into bacterial proteins. These proteins are then degraded and presented on MHC class I molecules. This presentation triggers a cytotoxic T cell response aimed at eliminating these cells, resulting in inflammation (myocarditis) due to the destruction of heart tissue.

This hypothesis aligns with observed cases of myocarditis post-vaccination, particularly in younger populations where the immune system is more reactive. The mechanism explains the localized inflammation in the heart through an immune attack on vascular muscle cells, which correlates with clinical findings of increased myocarditis cases after mRNA vaccination, as supported by data from vaccine safety monitoring systems.