Pfizer isn't subject to FOIA - the government is. To get approval for the vaccine to be sold, Pfizer submits a massive amount of documentation to the FDA. They

Pfizer isn't subject to FOIA - the government is. To get approval for the vaccine to be sold, Pfizer submits a massive amount of documentation to the FDA. They run studies with tens of thousands of patients and then do the typical statistics work to assess whether the vaccines were safe and effective (they were). They submit these studies along with all of the patient data collected during the trials and the FDA reviews the info to make their decision whether or not to approve the sale of the vaccine. These antivaxxers have decided that there must be something hidden in the patient files, so they filed a FOIA/lawsuit to have the FDA release all of these patient files. Those are the docs that would need to be scrubbed/anonymized. 450k pages of "Patient was administered vaccine, patient was fine".