Squalene is a natural molecule that humans and many other organisms produce. Humans require it as raw material for essential compounds such as hormones, and it can be found in some foods, cosmetics, and pharmaceutical products. Commercially, it is generally extracted from shark and other fish livers. Diets high in the compound may also lower cholesterol. Concerns that including the substance in vaccines is dangerous to health is not backed up by the World Health Organization (WHO) or the U.S. Food and Drug Administration (FDA).
Animals, including humans, produce the substance in the liver. It travels around in the bloodstream, and the body uses it to make necessary hormones and other compounds. Cholesterol is the intermediate step between the squalene and molecules such as estrogen, cortisol, and even vitamin D.
This particular molecule also leaches out from the body in our fingerprints. The livers of fish such as sharks are rich in the material, and this is where industries look for their sources. Apart from livers, it is also present in eggs, meat, and yeast.
Plants also produce the substance. For example, olive oil contains 0.7% squalene. The health benefits associated with the olive oil-rich diet of Mediterranean countries may be due to this feature of the oil. Health food enterprises sell it as "shark's liver oil." Some cosmetics contain the material, as do some medicines.
According to the FDA, the concentration of squalene in blood is generally at 250 parts per billion (250 nanograms per milliliter). Concerns that squalene in vaccines creates health risks are not substantiated by the WHO or by the FDA, as of 2011. The WHO says that a particular vaccine, which is administered in European countries, delivers a dose of 10 milligrams of squalene along with the antigen and that this vaccine has not presented any severe side effects since it was first produced in 1997.
The material is used in some vaccines to help make the immune system recognize the vaccination more efficiently. By itself, it is not effective, but when it is mixed up in an emulsion with other substances, it is. One issue that vaccine campaigners have with squalene is that soldiers who had been injected with an anthrax vaccine and who subsequently developed health problems showed antibodies to the substance in their blood. It is now known, however, that everybody has antibodies to squalene, which increase with age, and that the anthrax vaccine in question did not originally contain any of the substance. Tests that showed low levels of squalene in the vaccines may have been contaminated by laboratory glassware with fingerprints on them.