When you think of vaccines and their life-saving impacts, horseshoe crabs probably do not come to mind. But, these crustaceans found along the Atlantic and Gulf coasts are actually critical to developing countless safe and effective vaccines.
Horseshoe crabs have been around for about four hundred and fifty million years– making these “living fossils,” as some call them, even older than the dinosaurs.
And aside from seeing them scurry down the shore at most beaches on the east coast, these crabs have also played a part in likely every vaccine you have ever received.
More specifically, horseshoe crabs’ blood– which is a striking neon blue color– has been instrumental in testing the safety of vaccines on humans.
The species has been used to detect endotoxins– which can cause severe health complications, including anaphylactic shock and death– in vaccines and other injectable medicines given to humans for over thirty years.
This is possible because horseshoe crab blood contains crucial immune cells that are extremely sensitive to toxic bacteria. And whenever the cells encounter such toxins, the crabs’ blood will immediately clot around it in order to protect the rest of its body.
Scientists first recognized this in the 1970s and developed a groundbreaking test known as Limulus Amebocyte Lysate (LAL), which essentially vets new vaccines for contamination before administering them to the public.
And most recently, during the COVID-19 pandemic, over one hundred different vaccine iterations were being tested around the world. During that time, many researchers heavily relied on horseshoe crab blood and the LAL test to determine the safety and efficacy of the inoculation efforts.
But, while the species has substantially helped mankind avoid and/or curb pandemics in the past, horseshoe crabs themselves are not reaping the same benefits.