Derek Lowe has a post that discusses this.

In short from what I remember, the vaccine is administered in the deltoid, so most of the spike proteins should remain there. Some may travel throughout the body, but overall it is much much less than a natural infection.

That’s why I’m curious to compare myocarditis rates after vaccination to those after infection, because from what we know, natural infection should result in a higher rate of myocarditis than vaccination.