Essentially, they extended the original Emergency Use Authorization, (EUA) and revised it to allow the vaccine to be used more broadly. Anyone who says it is "fully approved" is simply incorrect.

They also updated the "Fact Sheet" for doctors to include warnings for previously-documented harmful side effects like myocarditis and pericarditis.

They also spend an entire page going over "safety data" from a variety of test groups. But none of these trials fit the FDA's own standard for approving a drug, since they have only been taking place in months, and normal FDA trials take several years at the minimum.

This is probably why they didn't formally approve it, and simply extended the EUA.

I will cite the most relevant parts of the article, and link the original at the bottom for anyone that wants to read it.

On August 23, 2021, having concluded that revising this EUA is appropriate to protect the public health or safety under section 564(g)(2) of the Act, FDA is reissuing the August 12, 2021 letter of authorization in its entirety with revisions incorporated to clarify that the EUA will remain in place for the Pfizer-BioNTech COVID-19 vaccine for the previously-authorized indication and uses, and to authorize use of COMIRNATY (COVID-19 Vaccine, mRNA) under this EUA for certain uses that are not included in the approved BLA

In addition, the Fact Sheet for Healthcare Providers Administering Vaccine (Vaccination Providers) was revised to provide updates on expiration dating of the authorized Pfizer-BioNTech COVID-19 Vaccine and to update language regarding warnings and precautions related to myocarditis and pericarditis

Having concluded that the criteria for issuance of this authorization under Section 564(c) of the Act are met, I am authorizing the emergency use of Pfizer-BioNTech COVID‑19 Vaccine for the prevention of COVID-19, as described in the Scope of Authorization section of this letter (Section II) and subject to the terms of this authorization. Additionally, as specified in subsection III.BB, I am authorizing use of COMIRNATY (COVID-19 Vaccine, mRNA) under this EUA when used to provide a two-dose regimen for individuals aged 12 through 15 years, or Page 5 – Pfizer Inc. to provide a third dose to individuals 12 years of age or older who have undergone solid organ transplantation or who are diagnosed with conditions that are considered to have an equivalent level of immunocompromise.

They also claim as one of their justifications for extending the EUA that

C. There is no adequate, approved, and available alternative to the emergency use of Pfizer-BioNTech COVID‑19 Vaccine to prevent COVID-19.

This appears to be misinformation, as India has already used Ivermectin to quell their surge, with very positive results. I won't go into the FDA leadership's ties to pharma companies as that is off topic for this post, but I personally think that is why they are so hell-bent on ignoring alternative treatments even after they were proven to have success in other countries.

The FDA announcement, for anyone that wants to read it for themselves: https://www.fda.gov/media/150386/download