Trawling for prey at more than a thousand feet under the surface, the scalloped hammerhead shark relies on a special oil in its liver to survive the crushing pressures of the deep.
Shark liver oil, or squalene, is a fatty substance that provides vital buoyancy for this critically endangered species and many others. But it’s also a lifesaver for humans as a boosting agent in vaccines, called an adjuvant, that improves the immune system and makes vaccines more effective.
As the world’s pharmaceutical companies scramble to create a vaccine for COVID-19, at least five of the 202 vaccine candidates rely on squalene sourced from wild-caught sharks. The Pfizer and Moderna coronavirus vaccines, which have both demonstrated early success, do not need adjuvants.
One candidate is a vaccine developed in Australia by University of Queensland, in partnership with the Australian biopharmaceutical company CSL and its subsidiary Seqirus. The as yet unnamed vaccine contains the squalene adjuvant MF59, which is sourced from a variety of shark species. It entered human clinical trials earlier this year and, if successful, will result in an initial production of 51 million doses.
Tens of millions of sharks are caught and traded internationally each yearboth legally and illegallythe majority for their meat and fins but roughly three million or more for their squalene. It takes the livers of between 2,500 and 3,000 sharks to extract about a ton of squalene.
Conservationists fear that increased demand for squalene for vaccines, among other uses, could further imperil shark species, a third of which are vulnerable to extinction.
This is an unsustainable demand to place on a finite natural resource like sharks, says Stefanie Brendl, founder and executive director of Shark Allies, a California-based conservation nonprofit. (Here are the most fascinating shark discoveries of the past decade.)
Only about one percent of squalene ends up in vaccines, and most goes into cosmetics such as sunscreen, skin creams, and moisturizers. Even so, as the global population booms, the need for vaccines will only increase in coming years, Brendl notes, adding that some medical experts suggest that people will require multiple doses of vaccines against COVID-19.
We’re not saying that vaccine trials should stop, but if we keep viewing sharks as an easy solution and don’t consider the alternatives that exist, then we’ll just continue to use [squalene] as a template for vaccines, Brendl says.
In light of declining shark populations, some biotech companies are looking for other sources of squalene. Plants such as sugarcane, olives, amaranth seeds, and rice bran, for instance, all contain the substance. While plant-based alternatives are being tested in studies and clinical trials, regulatory agencies such as the U.S. Food and Drug Administration have yet to approve them as part of a final vaccine product.
Joanne Cleary, a spokesperson for Seqirus, which uses the squalene adjuvant MF59, told National Geographic that their squalene is sourced from shark species that aren’t protected under CITES. In a follow-up request, Cleary did not say whether Seqirus’ suppliers meet sustainable fishing standards set by the Marine Stewardship Council.
Austin Gallagher, a National Geographic Explorer and chief scientist at Beneath the Waves, a Virginia-based shark-conservation group, says the pandemic has heightened public scrutiny of the vaccine-development process and exactly what goes into our medicines.
“One of the other significant things that also has come out of this pandemic, he says, has been simply shining a light on the greater environmental issue at hand here, which is the significant loss of sharks from our oceans that is happening at a global scale.
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