Danielle Pender
- Oct 4, 2020
- 2 min read

Why Are Horseshoe Crabs in the Coronavirus Vaccine?

Did you know that horseshoe crabs are a mainstay in vaccine development? The new coronavirus vaccines will be no exception. Vaccine developers use limulus amebocyte lysate (LAL), an enzyme extracted from the blood of Atlantic horseshoe crabs (Limulus polyphemus), to test for bacterial endotoxins in vaccines. Endotoxins are extremely dangerous to humans, causing fevers and even death, regardless of whether the bacteria producing them have been killed (Gorman, 2020).

How is the blood extracted from horseshoe crabs?

Every year, pharmaceutical companies collect horseshoe crabs from their habitat, extract their blood from a vein located near their hearts, and release them back into the ocean. In 2018 alone, biomedical facilities collected 464,482 crabs for blood extraction. This "catch and release" procedure claims to protect horseshoe crab populations, but recent estimates show that about 30% of horseshoe crabs die from this extraction, pushing Atlantic horseshoe crabs closer to endangered species status. According to the Wetlands Institute, Delaware Bay’s Horseshoe Crab population has declined by 90% over the last 15 years.

Enter rFC: a new test for vaccine endotoxin testing

In 2016, scientists discovered an alternative test for the blood, known as rFC (recombinant factor C), which was approved for use in Europe. Certain drug companies in the United States also began using the alternative. However, in June, the company behind the approval of rFC, U.S. Pharmacopeia, announced that rFC required much more study before it could be used. Representatives from the company state that rFC only has 2 years of data, compared to 30 years for LAL, rFC requires more information before widespread use. This decision will likely delay the usage of rFC by about 3 to 4 years, according to Dr. Jay Bolden, a biologist with Eli Lilly, a company aimed to replace animal use and reduce costs.

What's next for vaccine testing?

The debate of LAL vs. rFC is crucial during the development of new coronavirus vaccines. A new strain of vaccines has increased the demand for LAL, and billions of doses would require testing for endotoxins, putting horseshoe crab populations at risk.

Horseshoe crabs are an essential part of the Atlantic shore ecosystem, and several shorebirds depend on horseshoe crab eggs for nutrition.

Unfortunately, regulatory approval for rFC continues to drown in bureaucratic red tape. However, there are ways to support the horseshoe crab population. Find out more at the Wetlands Institute.

What do you think? Let us know in the comments!