Multiple studies from around the world have established that myocarditis is a rare but real risk associated with the mRNA COVID vaccines produced by Moderna and Pfizer. There has been no increased risk reported of the inflammatory condition with the Johnson and Johnson viral vector COVID vaccine. This fact should be mentioned to a person who is hesitant to receive a COVID-19 immunization based on concern about the myocarditis risk.
The J & J vaccine has its own risks not seen with the mRNA vaccines, particularly in women where abnormal thrombosis with thrombocytopenia has rarely been seen above background rates.
Let's look at cases of myocarditis reportedly caused by the mRNA vaccines.