from what I've gathered, the rate limiting step for production as of yet, is creating the lipid vesicles and getting the RNA inside of them. Only a few companies have a process for this, and the supply chain for the precursors is limited as well.
RNA would get thrashed by your immune system if it isn't encapsulated by something: liposome deliver of therapeutic RNA is really next-generation tech, and the fact that the RNA does what it's supposed inside the your cells is no small feat either.
From the CDC "ingredients" for the BioNTech/Pfizer vaccine, along with cholesterol (which modulates the stability of lipid membranes), they report using this molecule, which would form a phospholipid bylayer, just like our own cells use: https://www.sigmaaldrich.com/catalog/product/avanti/850365P?...
They're both encased in lipids. Pfizer didn't have long term data on long-term storage at standard freezer temperatures, but has since confirmed their vaccine can be stored at similar conditions to Moderna.
