Social media post misleads about flu vaccine ingredients. Here’s what’s in them.

The flu is going around this time of year, and so are misleading social media posts about the vaccines that prevent it.

As health officials recommend people age 6 and older get vaccinated to protect against severe illness from influenza viruses, some anti-vaccine advocates are issuing their own advisories. One such warning we saw gathering thousands of social media interactions included a purported list of "flu shot ingredients."

Included in the recipe, one such Instagram post proclaimed, are monkey kidney cells, antifreeze and human cell cultures from aborted fetuses. 

This Oct. 2 post was flagged as part of Meta’s efforts to combat false news and misinformation on its News Feed. (Read more about our partnership with Meta, which owns Facebook and Instagram.) We found other posts across social media using the same image or words.

Most of the ingredients included in the post are not used to make or produce flu vaccines used in the U.S., according to experts and product labels. A few of the listed ingredients are accurate, but the post fails to acknowledge that they are harmless or commonly used.

"Only a few ingredients listed on the image are in influenza vaccines," said Tina Proveaux, communications coordinator for the Institute for Vaccine Safety at Johns Hopkins Bloomberg School of Public Health. 

(Screengrab from Instagram)

There are nine influenza vaccines from four different manufacturers in use for the 2023-24 flu season in the U.S., according to a Centers for Disease Control and Prevention website, GSK, Seqirus, Sanofi Pasteur, AstraZeneca. Flu activity increases in October and peaks from December to February, according to the CDC.

There are different ingredients in each vaccine. But there are no antifreeze, monkey kidney cells or aborted human cell cultures in a list of influenza vaccine ingredients provided by the Institute for Vaccine Safety, a group that says it aims to provide an "independent assessment of vaccines and vaccine safety."

Nor are there any used as ingredients or in the production process, according to package inserts for each product. Those package inserts are available on a U.S. Food and Drug Administration website, and are linked to in the sources section of this story.

Human fetal cell lines and monkey cell lines have been used to produce vaccines against some other kinds of illnesses, but they are not used for vaccines that fight influenza.

The Children’s Hospital of Philadelphia said on its website that "no influenza vaccine available in the U.S. requires the use of fetal cells for production." Even if fetal cells are used to grow other vaccine viruses, the vaccines do not contain these cells or human DNA, the hospital said.

Antifreeze,  which is added to water in automobile cooling systems, commonly uses ethylene glycol, which is poisonous to humans, or propylene glycol, as ingredients. Propylene glycol is a chemical compound used as a food additive and in some medications. It has been used in the Pfizer and Moderna COVID-19 vaccines. 

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But neither ethylene glycol or propylene glycol are used in the flu vaccines.

The post misleads about some of the other ingredients, too, suggesting cells from dogs and insects are among them.

Seven vaccines use chicken eggs to grow the flu virus included in their formulas; two use different methods to grow the virus — one uses canine kidney cells and another uses insects in their production process, but not as ingredients, as the Instagram post falsely claims.

The Flucelvax Quadrivalent vaccine is the only cell-based flu vaccine in use in the U.S. That vaccine is manufactured using mammalian cells, specifically Madin-Darby canine kidney cells, from a line originating from a cocker spaniel’s kidney in 1958. A package insert for that vaccine said each dose of the vaccine "may contain residual amounts" of MDCK cell protein and cell DNA.

The only other egg-independent flu vaccine is Flublok Quadrivalent, which uses insect cells in its manufacturing. Flublok’s product sheet shows that residual amounts of cell proteins and DNA from the insects may be in the vaccine.

Some of the other ingredients the post’s list are used in flu vaccines, but are harmless. 

• Because most of the vaccines are produced using chicken eggs, there may be residual amounts of proteins from these eggs, including ovalbumin, in vaccine doses.

• Some flu vaccines use formaldehyde, an industrial chemical,  to kill viruses and inactivate bacterial toxins used to make the vaccines. Formaldehyde has been shown to cause cancer in lab animals, but the FDA and the CDC said any residual formaldehyde found in vaccines is lower than the amount found naturally in the human body and poses no safety concern.

• Thimerosal is an ethylmercury-based preservative that is used only in multi-dose packages of flu vaccines to prevent contamination. It was removed from use in children’s vaccines in 2001 as a precautionary measure. Ethylmercury decomposes, passes through the body quickly and does not cause mercury poisoning. The vast majority of flu vaccines don’t contain thimerosal. People concerned about thimerosal can request a flu vaccine that doesn’t contain the preservative, the Centers for Disease Control and Prevention said.

• Porcine gelatin is listed as an ingredient in AstraZeneca’s FluMist nasal spray. That comes from collagen in pigs and is often used as a stabilizer in vaccines. 

• "Detergent" is a far-reaching term for surfactants, which are chemical compounds that decrease surface tension in liquids. They are used in cleaning detergents, cosmetics, and food, such as ice cream. They are also commonly used in vaccines to blend ingredients together and prevent settling. Some surfactants, such as Polysorbate 80 and sodium Deoxycholate, are listed as being used in flu vaccines. 

An Instagram post claimed that flu vaccines contain aborted human cell cultures, monkey kidney cells and antifreeze.

An examination of ingredients and descriptions of the production process for each of the nine flu vaccines used this year in the U.S. shows that’s inaccurate. A few other ingredients listed in the Instagram post, such as canine and insect cells, formaldehyde and gelatin are used to make flu vaccines, but most ingredients listed in the post are not in the vaccines.

We rate the claim False.