Shark liver oil, or squalene, is a fatty substance that is considered a lifesaver for humans. It acts as a boosting agent in vaccines, called an adjuvant, that improves the immune system and makes vaccines more effective.
The importance of shark liver oil has further increased now, amidst the ongoing Covid-19 pandemic, as pharmaceutical companies around the world are working on various coronavirus vaccines.
At least five of the 202 Covid-19 vaccine being made by various pharmaceutical companies around the world are relying on squalene, sourced from wild-caught sharks.
However the Pfizer and Moderna coronavirus vaccines, which have both demonstrated early success, do not need adjuvants.
Tens of millions of sharks are caught and traded internationally every year, both legally and illegally, the majority for their meat and fins.
But roughly three million or more sharks are caught 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.
Only about one percent of squalene ends up in vaccines, and most goes into cosmetics such as sunscreen, skin creams, and moisturizers.
As the global population booms, the need for vaccines will only increase in coming years. Some medical experts suggest that people will require multiple doses of vaccines against COVID-19.
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 US Food and Drug Administration have yet to approve them as part of a final vaccine product.
For centuries, people have exploited shark livers for food and energy - liver oil, for example, fueled streetlights across 18th-century Europe.
The oil has also long been used in textiles and food coloring, as well as cosmetic products.
But it wasn’t until 1997 that Chiron, a former biotech company that's since been acquired by Novartis, used squalene as an adjuvant in the FLUAD influenza vaccine.
Other major pharmaceutical companies, such as GSK and Novartis, began to rely on squalene for their seasonal flu and swine flu vaccines.
