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.

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