Several companies in the race for a coronavirus vaccine have stumbled upon a new and unexpected hurdle: activists protesting using a substance that comes from sharks in their products.
The oily compound, called squalene, is churned out by shark livers and has immunity-boosting powers, which has led several companies to use it as an ingredient in vaccines. Shark Allies has mounted a campaign calling on the Food and Drug Administration and other regulatory bodies to halt the sourcing of the compound from sharks, warning that mass distribution of a coronavirus vaccine could require harvesting tissue from more than 500,000 sharks.
The call to action made headlines around the globe. But the story on shark squalene isn’t as clear-cut as it might at first seem.
Why are some people so upset about sharks and vaccines?
Companies commonly use squalene as a moisturizing additive in cosmetics and sunscreens. But the substance has also been occasionally used in vaccines as an adjuvant — a chemical that kick-starts the immune system into action, driving stronger, longer-lasting protection against disease.
Although adjuvants aren’t necessary for all vaccines, they can make or break certain recipes. By boosting products’ immunity-priming powers, they can also increase the immunization’s efficiency, giving the vaccine’s ingredients more bang for their buck and freeing up supplies for more doses.
Shark livers are considered among the best sources of the compound. According to Catherine Macdonald, a shark biologist in Florida, between 63 million and 273 million sharks die at the hands of humans each year, and liver oil is harvested from at least a couple million of them.
Two of the companies under the scrutiny of Shark Allies are GlaxoSmithKline and Seqirus, which each manufacture adjuvants that contain about 10 milligrams of squalene per dose. Those ingredients are found in several coronavirus vaccines being tested in humans, including products from Sanofi, Medicago, and Clover Biopharmaceuticals, all partnered with GSK.
According to one estimate, between 2,500 and 3,000 sharks are needed per metric ton of squalene. Shark Allies extrapolated from these statistics to arrive at their widely quoted numbers tabulating the sharks’ potential ecological toll.
Are Shark Allies’ numbers realistic?
Such estimates are difficult to make.
Macdonald pointed out that sharks — of which there are more than 500 species worldwide — vary in size, weight, and liver squalene content. The number of sharks required to yield enough squalene-adjuvanted vaccine doses to treat everyone on Earth is thus likely to be a “huge range,” she said. Her own calculations for this statistic stretch between tens of thousands and more than 1 million, depending on how many doses are needed per person.
It’s also the case that most don’t include squalene of the dozens of vaccine candidates in clinical trials in people. To only rely on vaccines that use shark-based squalene, “a ton of other promising candidates would have to fail — they would have to be the last vaccines standing,” said Saad Omer, a vaccine expert at Yale University. A more plausible scenario would probably involve the distribution of several products made by multiple companies.
Are there alternatives to shark oil?
Squalene has plenty of plant and animal sources (including humans, who produce it to lubricate and protect their skin).
But squeezing squalene out of plants is a pain, while “shark oil is cheap and easy to come by,” said Stefanie Brendl, the executive director of Shark Allies.
“We feel that’s not an excuse,” she said.
She pointed to Amyris, a California-based company, which has been pursuing a synthetic alternative.
Evan Berland, director of U.S. corporate communications for GSK, said the company “is committed to environmental stewardship and is actively exploring the potential for alternative sources of its raw materials when possible.”
However, no squalene alternatives would be available “within the time frame of the COVID-19 pandemic,” he said.
Joanne Cleary, a Seqirus spokeswoman, said her company was in a similar situation. “More will need to be done to research plant-based or synthetic alternatives before they can be used in vaccines,” she said.
Swapping adjuvants, or even adjuvant sources, isn’t trivial, Omer said. Each product must be refined and tested to ensure it’s safe and effective and work its way — often ploddingly — through the necessary regulatory steps.
Are vaccine makers to blame for harvesting shark squalene?
Neither GSK nor Seqirus named their suppliers. But GSK said the sharks their squalene came from were “typically caught for other purposes.”
Macdonald said it’s impossible to answer questions about the exact number of sharks that would be killed explicitly for their squalene. Fishers capture sharks for their meat or fins or simply as bycatch; in many cases, the oil pulled from their bodies might otherwise have been discarded.
So should you really worry that coronavirus vaccines will result in a mass culling of sharks?
Even the Shark Allies team does not think the vaccine industry is “going out and hunting down sharks — we are not saying that at all,” Brendl said. Nor do they wish for companies to terminate or delay coronavirus vaccine production.
“But there are alternatives to shark adjuvants,” she said. “Start testing them.”
Macdonald and others noted that vaccine manufacturers by no means bear the brunt of the responsibility for hoarding shark liver oil. Most fish-sourced squalene is still routed to cosmetics — “much less important things” than vaccines, said Jasmin Graham, a shark biologist at Mote Marine Laboratory in Florida.
Crafting more sustainable fishing practices, she said, could help tackle multiple issues at once.
“I don’t think we should demonize the people trying to save our lives,” Graham said. “There are much larger, more important hills to die on.”