[minifridge]

Immunity does not mean mRNA molecules diffused across the body. The mRNAs are supposed to be translated and degrated yielding the antigen protein. This antigens cause inflammation at the area of injection and in theory only the protein antigen will be circulated by the immune cells to generate immunity.

[wesapien]

I'm recalling from a podcast that intramuscular shots doesn't really isolate but rather slows down the actual spread within the body. There's still capillaries and the lymphatic system where the shots can travel. How else do we explain what is happening?