Viral post claiming to show 'harmful ingredients’ in flu vaccine is misleading

What's the claim?

A viral post circulating on Facebook claims flu shots contain ingredients such as mercury, formaldehyde, and porcine (pig) arginine. After gaining traction in 2023, the claim spread across other platforms, including Instagram and X (formerly Twitter), fueling misinformation about vaccine safety.

While the Facebook post lacks a caption, the version on X states, “If you fed that to someone on a spoon, you could be done for attempted murder. But somehow, it’s okay to inject it into a person’s body without telling them what’s in it. Note: Mercury is toxic to humans in ANY quantity.”

Screenshot of the viral post. (Source: X/screenshot)

However, the claims made in the Facebook and X posts are misleading. Experts confirm that many of the listed ingredients are not present in any flu vaccine.

So, what’s in a vaccine? 

Vaccines consist of fragments of disease-causing organisms or their parts, known as antigens, which help the body learn to fight the disease without causing illness. They also contain other ingredients, including preservatives, stabilizers, surfactants, residuals, diluents, and adjuvants:

1) Preservatives, such as thimerosal, are used to prevent bacterial and fungal growth in stored vaccine preparations.

2) Stabilizers, which can include sugar or gelatin, help prevent chemical reactions within the vaccine.

3) Surfactants ensure the ingredients remain blended and are also found in ice cream.

4) Dilutants, such as sterile water, maintain the vaccine's consistency. 

5) Adjuvants, like aluminum salts, enhance the vaccine's safety and effectiveness from the manufacturing plant to the point of use.

Virologist Dr. Shahid Jameel, a fellow at Green Templeton College, University of Oxford, and a visiting professor at Ashoka University, told Logically Facts, “Adjuvants boost the body’s immune response to vaccines. The most popular and inexpensive ones are aluminum salts, such as aluminum hydroxide and aluminum phosphate. These are used in all vaccines—not just flu vaccines—and have been in use for over 70 years.”

He further explained that “stabilizers are added to vaccines to ensure effectiveness throughout their recommended storage period. Stabilizers are widely used in the pharmaceutical industry, not just in vaccines.”

Addressing concerns about gelatin, he stated, “Traditionally prepared from animal collagen, there is now a significant shift away from animal sources.” Other stabilizers may include polysorbate, which is also used in the food industry.

Thimerosal in vaccines differs from the mercury that causes mercury poisoning, according to the Centers for Disease Control and Prevention (CDC). The World Health Organization (WHO) also states that there is no risk associated with thiomersal, a preservative that has been closely monitored for safety in vaccines.

Dr. Jameel clarified that thimerosal, a compound containing mercury, is used in trace amounts in vaccines to prevent bacterial or fungal growth and is not harmful at these levels.

What’s in a flu shot? 

The Vaccine Knowledge Project, an academic research group in the Department of Pediatrics at the University of Oxford, provides more information on influenza vaccine ingredients.

In the UK, inactivated flu vaccines often contain very small amounts of sodium and potassium salts (used as acidity regulators), polysorbate (an emulsifier that holds other ingredients together), antibiotics (gentamicin, neomycin, kanamycin, or polymyxin) to prevent bacterial contamination, and formaldehyde (used to inactivate or kill viruses).

The Institute for Vaccine Safety, an independent organization that assesses vaccine safety, lists thimerosal as a preservative, formaldehyde as an inactivating agent, aluminum as an adjuvant, and polysorbate as a surfactant in influenza vaccines.

The list does not include ‘monkey kidney cells’ or ‘aborted human cell cultures.’ So, why does the post mention them? This confusion stems from the fact that some vaccines use fetal cell lines to grow viruses. However, these vaccines do not contain actual fetal cells or tissues.

Dr. Jameel explained that “unlike bacteria, viruses cannot be grown in synthetic media,” so human and animal cells are necessary for cultivating them. Once the viruses have grown in large quantities, they are purified from the culture media and thoroughly washed.

We also examined other ingredients mentioned in the post, such as antifreeze, which is ethylene glycol. This compound is harmful to health but is often confused with polyethylene glycol, a safe ingredient used in vaccines, skincare products, and toothpaste. The American Academy of Pediatrics has debunked this misconception.

When it comes to the presence of formaldehyde, the claim has been debunked multiple times. There’s more formaldehyde found naturally in our bodies than there is in vaccines. According to the Vaccine Knowledge Project’s list of vaccine ingredients, “formaldehyde in a 2-month-old infant’s blood is ten times greater than the amount found in any vaccine.”

Another listed ingredient is aluminum, which is safe and used in some vaccines. In fact, aluminum is one of the most common elements in the Earth’s crust and is present in almost all our food. 

Dr. Jameel explained how the flu shot is manufactured. “Flu vaccines deploy influenza viruses that have been grown either in fertilized eggs or on animal/human cells in culture. Live vaccines (nasal spray type) use weakened flu viruses that raise immunity without causing disease. Inactivated vaccines (injection type) use regular flu viruses that are grown in large amounts, purified, and inactivated.” 

The U.S. FDA also discusses the common ingredients present and how safe they are. In fact, every vaccine’s package insert lists the ingredients, which are also available on the FDA website.

The verdict

The claim about flu shot ingredients is misleading, as many listed items are not present in vaccines. Additionally, many of the products mentioned are not harmful to human health. Vaccines are generally safe and undergo rigorous testing before being rolled out. For more information on the safety of flu vaccines, visit the CDC website.