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yesterday

Study Identifies Likely Mechanism for Rare Myocarditis After mRNA COVID Vaccination

The preclinical results suggest testable ways to prevent or blunt the reaction without reducing vaccine benefits.

Myocarditis. Light micrograph of human cardiac muscle with chronic myocarditis (inflammation). In this longitudinal section, muscle fibres run diagonally (purple). Abnormal features are a loss of organisation of the muscle fibres which are normally closely spaced, with the spaces between fibres (white, blue) representing oedema. There are neutrophils (white blood cells, purple dots) infiltrating the oedematous areas, as an early inflammatory response and to prevent infection. Chronic myocarditis is caused by rheumatic fever and virus infections, with enlargement of the heart. Magnification: x50 at 35mm size. https://www.sciencephoto.com/media/257798/view
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Overview

  • Experiments published in Science Translational Medicine point to CXCL10 and interferon gamma as key inflammatory drivers in lab models of post‑vaccine heart inflammation.
  • Lab-made human immune cells exposed to mRNA COVID vaccines showed surges in these cytokines, mirrored by elevated levels in vaccinated young male mice.
  • Injecting the isolated cytokines into mice and human cardiac spheroids produced tissue damage and impaired function, which improved when cytokine-blocking drugs were applied.
  • Treatment with genistein, a plant-derived estrogenlike compound, prevented damage in mice and cardiac spheroids, supporting a hypothesis that sex hormones may influence risk.
  • The condition remains uncommon—about one case per 140,000 first-dose recipients—and typically resolves with supportive care, while COVID-19 infection poses a higher and often more severe risk of heart complications.