I have some sources here at the bottom of my employer letter:

Dear xxx,

I received notice that the COVID-19 vaccine is FDA approved and that you are requiring the vaccination for continued employment. I would be happy to take the vaccine. On advice of my attorney xxx (my sister-in-law, but you can use a doctor or whoever) it was recommended that I should opt to take the FDA approved vaccine called Comirnaty for legal reasons. On further review, however, it appears that the FDA vaccine is not available yet in the US. Please see the sources below this letter. Could you provide an exception for this until the vaccine comes onto the market. It was indicated by the justification for the company mandate that the vaccine is FDA approved and I would therefore be more comfortable taking the FDA approved vaccine.

Thank you, xxx

My lawyer can be contacted at: xxx xxx

Sources:

1. From a letter to the FDA from the US Senate:

https://www.documentcloud.org/documents/21054683-sen-johnson-letter-to-fdas-woodcock

In the letter that reissued the EUA for the Pfizer-BioNTech COVID-19 vaccine, the FDA stated that Comirnaty and the Pfizer-BioNTech COVID-19 vaccines are “legally distinct with certain differences that do not impact safety or effectiveness.”4 That statement, together with the fact that the FDA issued two distinct letters – one extending the EUA for the vaccine used in the U.S. and the other granting the FDA approval of the Comirnaty vaccine used in Europe and other countries – has caused a great deal of confusion.

As I stated to you in my letter dated August 22, 2021, “I see no need to rush the FDA approval process for any of the three COVID-19 vaccines. Expediting the process appears to only serve the political purpose of imposing and enforcing vaccine mandates.”5 Because the FDA-approved Comirnaty vaccine is not generally available in the U.S., but the Pfizer-BioNTech COVID-19 vaccine will continue to be used in the U.S. under a reissued EUA, the FDA seems to be confirming my suspicion.

2. News article dated Sept 3, 2021 - "Newly Approved COVID-19 Vaccine Not Yet Available in US":

https://www.theepochtimes.com/newly-approved-covid-19-vaccine-not-yet-available-in-us_3976794.html

The FDA and the Centers for Disease Control and Prevention (CDC) declined to answer or did not respond to questions about when the approved vaccine, dubbed Comirnaty, would be available.

Pfizer did not answer directly when asked and BioNTech did not return an inquiry.

But health officials from states across America confirmed to The Epoch Times that they do not have any Comirnaty doses, and that none are expected soon.

“Comirnaty-labeled doses are not yet in circulation in the U.S. yet,” a spokesman for the Arizona Department of Health Services told The Epoch Times in an email.

“There is no timeline for when the branded product will start to be shipped,” a spokeswoman for the Tennessee Department of Health added.

An official in Massachusetts said that the approved doses are not likely to be distributed until October, at the earliest.

Georgia, Illinois, North Dakota, West Virginia, Wyoming, and Washington state have also not received any Comirnaty doses, officials said.

3. From an article dated September 14, 2021 from Lynnwood Times:

https://lynnwoodtimes.com/2021/09/14/is-the-pfizer-vaccine-fda-approved/

"On August 23, the FDA did grant its approval for a COVID-19 vaccine, but potentially not a labeled FDA-approved vaccine that is currently available for distribution."

5. FDA indicates that the two Pfizer products are "legally distinct":

https://www.fda.gov/vaccines-blood-biologics/qa-comirnaty-covid-19-vaccine-mrna

Comirnaty has the same formulation as the FDA-authorized Pfizer-BioNTech COVID-19 vaccine and can be used interchangeably to provide the COVID-19 vaccination series without presenting any safety or effectiveness concerns. The products are legally distinct with certain differences that do not impact safety or effectiveness.

6. FDA indicates that the BNT162b2 EUA Pfizer vaccine has a different composition than the Comirnaty vaccine - https://web.archive.org/web/20210913042547/https://www.fda.gov/media/151733/download

see page 14: 4. NonclinicalPharmacology/Toxicology

"COMIRNATY and BNT162b2 (V8) have identical amino acid sequences of the encoded antigens but COMIRNATY includes the presence of optimized codons to improve antigen expression."

7. FDA indicates on its definition page that same formulation does not mean same composition:

https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm?fr=314.3

Sec. 314.3 Definitions.

Same drug product formulation is the formulation of the drug product submitted for approval and any formulations that have minor differences in composition or method of manufacture from the formulation submitted for approval, but are similar enough to be relevant to the Agency's determination of bioequivalence.

Bioequivalence is also defined on that page:

Bioequivalence is the absence of a significant difference in the rate and extent to which the active ingredient or active moiety in pharmaceutical equivalents or pharmaceutical alternatives becomes available at the site of drug action when administered at the same molar dose under similar conditions in an appropriately designed study. Where there is an intentional difference in rate (e.g., in certain extended-release dosage forms), certain pharmaceutical equivalents or alternatives may be considered bioequivalent if there is no significant difference in the extent to which the active ingredient or moiety from each product becomes available at the site of drug action.

The definition includes extended-release dosages and alternatives. The terminology appears to be fairly loose. Same formulation means that it may have a different composition and delivery mechanism but it's bioequivalent if the right active ingredient goes to the right places. According to the above definition it could be a completely different alternative drug and still be a 'same formulation'. However, the main concern is that the two vaccines are "legally distinct" and may come with different legal consequences.