In the bid to find a Covid-19 vaccine wildlife experts claim half a million sharks could be slaughtered for the much anticipated jab.
Squalene, a natural oil made in the liver of sharks, is used medicine and is also used as an adjuvant to increase the effectiveness of a vaccine.
It is also being used in trial vaccines for the coronavirus.
If a drug passes that contains squalene and goes into production across the world conservationist group Shark Allies believe around 250,000 sharks will need to be slaughtered to provide one dose for each person.
That figure doubles and becomes more dire if people need two shots instead of one to fully vaccinate against Covid-19.
Stefanie Brendl, founder and executive director of Shark Allies, said: "Harvesting something from a wild animal is never going to be sustainable, especially if it's a top predator that doesn't reproduce in huge numbers."
In a Facebook post, she added: "We are not trying to slow down or hinder the production of a vaccine.
"We simply ask that testing of non-animal derived squalene is conducted alongside shark squalene so it can be replaced as soon as possible.
"At billions of doses needed per year, for decades to come, it is critical that we don't rely on a wild animal resource. It can be detrimental to shark species that are hunted for their oil, and it is not a reliable supply chain."
The group has set up an online petition named 'Stop Using Sharks in COVID-19 Vaccine - Use EXISTING Sustainable Options'.
Their target for signatures was 10,000 - they've already reached 9,500.
They say there are alternatives as the chemical structure of the squalene compound is identical in sharks and non-animal alternatives, meaning its effectiveness in vaccines should be identical regardless of its source.
There are 40 vaccines for Covid-19 in clinical evaluation and 142 vaccines in preclinical evaluation, say the World Health Organisation (WHO).