A new study published in Science Translational Medicine has demonstrated a new mechanism by which mRNA COVID vaccines can cause heart inflammation, or myocarditis, in young men.
While rare, myocarditis is a documented side effect that can occur after receiving an mRNA COVID vaccine. To study why this effect might occur, researchers collected blood samples from individuals who had received the mRNA vaccine, including a subset of individuals who developed myocarditis. When blood samples were compared between people who had and had not developed myocarditis, two immune signaling proteins stood out in the samples of individuals with myocarditis. The researchers further tested the effects of these proteins by vaccinating male mice and observing the levels of the two proteins as well as any damage to their hearts. The mice showed heart damage after vaccination due to immune cells infiltrating their hearts. However, when the two proteins were blocked, the damage was limited. These results confirmed that a heightened immune response was causing heart inflammation in some individuals after vaccination.
Myocarditis is exceptionally rare after the mRNA COVID vaccine; it affects about one out of 140,000 individuals after one dose, and about one out of 32,000 individuals after a second dose. Rates of myocarditis after vaccination are highest in males who are 30 years old or younger, who are affected at a rate of about one per 16,750 individuals. Symptoms generally occur one to three days after vaccination and can include shortness of breath, palpitations, chest pain, and fever. While most cases are mild and resolve naturally, severe cases can lead to injury, hospitalization, and even death. While myocarditis can occur in both men and women after vaccination, the authors believe that estrogen may provide a mildly protective effect in women due to its anti-inflammatory effects. For this reason, soy-derived compounds that have a similar structure to estrogen may help prevent myocarditis after vaccination and are currently being investigated.
Sources: Science Translational Medicine, Science Daily
