The reason the mRNA method is so attractive is because large amounts can be manufactured more quickly than a traditional protein based antigen approach.
The mRNA vaccine has a lot of questions about the mechanism. Not really the mechanism that produces the antigen (spike protein) per se, but the cell types that take up the mRNA to begin with. What cell types take up the RNA? How long do those cells crank out antigen? How long does it take for that mRNA to degrade? Does the host cell die after a time? Is the antigen released from the cell or does the cell present the antigen as non self though MCH class II mechanisms?
I've tried to get answers for these questions, but to no avail. I know people at pfizer, and I've asked them directly. Either they wont say because of proprietary reasons, or they don't know. My feeling is a lot of the latter. Not knowing the answers to the above questions wouldn't necessarily make it unsafe. Safety data doesn't really hinge on knowing exact mechanisms sometimes, but it would be nice to know.
As a healthy adult with zero underlying conditions, and the fact I've been out from under the bed for 6 months at work, in restaurants, on public transport, etc, I'll take my chances with the Rona for awhile longer until more people get dosed up with it and see if they grow extra limbs.
Lava Rock may know a little more since vaccines are more up his alley than mine. I'm an immunologist and pathologist, but I make cancer drugs, not vaccines.