I would like to understand what exact processes make intramuscular injection of particularly mRNA covid vaccines the best delivery option. I've asked doctors and googled, but I get contradictory responses.
My understanding is that muscle cells are predominantly affected, causing an intentionally localized inflammation, and use the mRNA to produce spike protein which immune cells then pick up and navigate to lymph glands, which are close to the injection site, for antibody production.
In contrast, a couple of doctors told me that "intramuscular delivery is just a way to make the vaccine slowly seep into the bloodstream" and that "muscle cells are not affected, the vaccine targets immune cells to prompt antibody production".
Please help me grasp the basics. Sources very welcome!