My apologies... I now understand.
They are creating the mRNA sequence that is used by the ribosomes to create the spike protein that is the antigen. You are correct, they are not directly creating the antigen, but are indirectly creating it by creating the recipe in the mRNA.
Thank you for challenging me. I am always willing to learn.
You beat me to it by 8 seconds... and you are correct. This actually is elegant because it works just like the virus, except you dont get infected, just immunity.