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Andy Nguyen
By Andy Nguyen October 1, 2021

A redacted ingredient of the Pfizer COVID-19 vaccine is just water

If Your Time is short

  • The Pfizer vaccine does not contain a mysterious ingredient undisclosed to the public. 
  • The Pfizer vaccine and those from Moderna and Johnson & Johnson have been safely given to tens of millions of people around the United States.

An Instagram post claimed the COVID-19 vaccine from Pfizer contains an undisclosed mystery ingredient, even though the full ingredient list has been available online since December 2020.

The Sept. 20 post shows a table from the federal Food and Drug Administration titled "composition of COMIRNATY Multiple Dose Vial." Comirnaty is Pfizer’s brand name for its COVID-19 vaccine.

The table shows the different ingredients that make up the vaccine, according to the Instagram post. However, one of the listed ingredients, described as an excipient, is redacted. 

The caption on the post claimed the excipient, a type of inert substance that acts as a vehicle for a drug, makes up 20% of the vaccine and could potentially make up 20% of each dose.

"The undisclosed ingredient is also not disclosed in the vaccine package insert," the post said. "If the American people don't know the identity of an ingredient in an FDA-approved vaccine, how is informed consent possible?"

The post was flagged as part of Facebook’s efforts to combat false news and misinformation on its News Feed. Instagram is owned by Facebook. (Read more about our partnership with Facebook.)

Although not all the ingredients of the vaccine were shown in that FDA document, the ingredients of the vaccine are not undisclosed. They have been public since the vaccines came out.

Early version of report

The table featured in the post comes from the FDA as part of a summary report explaining its decision to give final approval to the vaccine. The report includes the studies conducted on the vaccine and an ingredient list.

Although an earlier version of the report had one ingredient redacted, as shown in the Instagram post, the FDA updated the report since the post, removing the redaction.

The formerly redacted ingredient is listed as "water for injection." (A Sept. 30 update to the Instagram post acknowledged the change.)

Featured Fact-check

Pfizer’s vaccine is distributed in vials of a frozen suspension that must be thawed and diluted with a sterile saline solution of a certain concentration to produce several injectable doses. The table on the FDA report lists the ingredients and their amounts "after dilution." 

The package insert for the vaccine lists the ingredients of the suspension and includes the dilution instructions: "Dilute the vial contents using 1.8 mL of sterile 0.9% Sodium Chloride Injection, USP to form COMIRNATY. Do not add more than 1.8 mL of diluent." The insert also details the clinical trials on the vaccine and their findings.

Redactions in FDA reports

Redactions do occur in FDA reports, and are usually for information that’s considered a confidential or trade secret, said Alison Hunt, a press officer for the FDA.

The FDA report on Pfizer’s vaccine still has some redacted information, but Pfizer says it involves "proprietary pieces of the lipid nanoparticle that makes it unique" to the company. Lipid nanoparticles are a type of fatty material that helps transport the vaccine's active ingredient into a person's cells.

Claims that the COVID-19 vaccines contain mysterious or harmful ingredients are not new. They have been checked several times by PolitiFact, and rated False. The ingredients list for the Pfizer, Moderna and Johnson & Johnson vaccines have been available online from the FDA, without redactions, since the vaccines became publicly available.

Our ruling

An Instagram post claimed the Pfizer COVID-19 vaccine contains an undisclosed ingredient.

The post cited an FDA report in which one of the ingredients listed was redacted. The agency has since updated the file and revealed that the ingredient was water.

Long before the FDA report, the ingredients of the Pfizer vaccine, as well as ones for the Moderna and Johnson & Johnson vaccines, were made public online, without any redactions.

We rate this vaccine claim False.

CORRECTION (Oct. 11, 2021): An earlier version of this fact-check included an incorrect date for when this Instagram post was made. It was correct in the body of the fact-check but wrong in the header and has been corrected.

Our Sources

Instagram post, Sept. 20, 2021

Merriam-Webster, definition of excipient, accessed Sept. 29, 2021

FDA, Summary Basis for Regulatory Action for Comirnaty vaccine, Aug. 23, 2021

FDA, Package Insert - COMIRNATY, accessed Sept. 30, 2021

Email with FDA Press Officer Alison Hunt, Sept. 29, 2021

Email with Pfizer Media Relations, Sept. 29, 2021

PolitiFact, "10 types of COVID-19 vaccine misinformation swirling online, fact-checked," July 26, 2021

PolitiFact, "The COVID-19 vaccines do not contain aluminum," March 22, 2021

PolitiFact, "No, the new coronavirus vaccines are not more dangerous than COVID-19," Dec. 18, 2020

PolitiFact, "No, the Moderna vaccine does not contain an ingredient that’s for "research use only," May 21, 2021

FDA, Pfizer COVID-19 vaccine fact sheet for recipients and caregivers, accessed Sept. 30, 2021

FDA, Moderna COVID-19 vaccine fact sheet for recipients and caregivers, accessed Sept. 30, 2021

FDA, Janseen, Johnson & Johnson COVID-19 vaccine fact sheet for recipients and caregivers, accessed Sept. 30, 2021

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A redacted ingredient of the Pfizer COVID-19 vaccine is just water

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