Millions of doses of the H1N1 vaccine contain a substance extracted from shark livers, prompting activists to worry that the vaccine may be putting a threatened species at risk. Commonly found in beauty products like skin creams, squalene is primarily harvested from sharks, especially deepwater species; it can also be used to make an adjuvant, which boosts the body’s immune response. Vaccines containing squalene have yet to be approved in the U.S., but have been distributed elsewhere, including Canada and Europe, National Geographic reports. GlaxoSmithKline (GSK), a major H1N1 vaccine producer, said in October it had received orders for 440 million doses of adjuvant-containing vaccine. The adjuvant contains shark-liver squalene, one spokesperson confirmed. Deep-sea sharks that provide this, found from 300 to 1,500 meters, are most often caught by bottom trawling, “a horribly destructive fishing method that just bulldozes everything in its path and destroys enormous areas of the ocean floor,” says Mary O’Malley, co-founder of the volunteer-run advocacy group Shark Safe Network. Deepwater sharks, which are at risk, are slow-growing and rarely reproduce, she added. While some cosmetics firms have stopped using shark squalene, an alternative isn’t yet an option for adjuvant vaccine makers, GSK said, although it is looking at other sources, including olive oil.