WALL STREET JOURNAL: Covid-19 Vaccines and Myocarditis Link Probed by Researchers: Several theories are under investigation seeking to explain heart-inflammation conditions among small numbers of vaccinated.

The spike protein helps the virus gain entry into human cells to replicate. The mRNA vaccines are designed to cause the body to make a certain version of the spike protein, which then sets off an immune response.

The immune response includes neutralizing antibodies that target the spike protein and thereby block the virus’s ability to get inside cells and replicate. The immune response can protect a person against Covid-19 or lessen its severity if someone is exposed to the virus.

Yet there may be similarities between the spike protein and proteins found in the heart muscle, prompting the body’s immune defenses to mobilize against the heart, according to Biykem Bozkurt, a professor of medicine specializing in cardiology at Baylor College of Medicine in Houston. . . .

Some doctors have theorized that improper injections of the vaccines may be contributing.

The shots are supposed to be injected into the shoulder muscle, also known as the deltoid muscle. If the injection accidentally reaches a vein, it could lead to delivery of some of the vaccine to the heart through blood vessels.

I suppose a subcutaneous injection wouldn’t be an alternative, because the shots have to enter muscle tissue to work.