The way I explain this to young children is that the mRNA vaccines are like injecting a Xerox machine into you that is programmed to only make 5 copies of a protein goobledeegook that looks suspiciously like the spike protein on SARS-COV-19 but is not, in fact, said protein goobledeegook. After making 5 copies, it peaces out. There is really no pharmacological difference between the Pfizer and Moderna vaccines. Both are miraculous innovations, and the biotech they're built on will revolutionize medicine. It's basically a DVD player where you can just input different DVDs/viruses and press play. It's so nice to be alive!