What are the modified RNA bases in mRNA Covid vaccines and/or how are the metabolised in the human body ? Have you heard about any safety issues with these modified bases ?
For Pfizer, I know, that the modified bases are 1-methyl 3'-pseudouridine. From there, wikipedia directs me to the page on pseudouridine, which is naturally present in tRNA. However, it is not the same chemical. I do not know how easy or difficult for the human body is to remove the methyl moiety.
For Moderna, I do not know what are the modifications at all.
The reason I am worried: I have seen an unsourced claim on facebook, that Moderna has had a problem getting approved several of their products, because of the toxicity of the modified bases. Maybe it is a failure mode, letting an unsourced claim start a process of worrying and searching the information on the modified bases. But the process has already started in my head... I would very much appreciate some details, if you guys know them. (Apart from the obvious info, that the clinical trials did not show any short od medium- term problem).