I found out about this from the letter the FDA sent Pfizer on August 21, 2021. Here’s the link. https://www.fda.gov/media/151710/download
In other news most of Senator Johnson’s Republican colleagues were unavailable for comment, most hiding under their desks or being entertained by big pharma lobbyists.
Your linked letter indicates that “BNT162b2”/”Tozinameran” (original 2 names from last year) and “Comirnaty” (new “Brand Name” after FDA approval) are all the same compound/vaccine. Refer to quoted trials of “BNT162b2” in the letter.
https://clinicaltrials.gov/ct2/show/NCT04380701
https://clinicaltrials.gov/ct2/show/NCT04368728