Coronavirus vaccine search runs on horseshoe crab blood

A horseshoe crab shares the coastline with red knots at Delaware’s Mispillion Harbor.
Credit: Gregory Breese/USFWS

Testing for dangerous bacteria called endotoxins in vaccines and other medicines has long relied on a component in horseshoe crab blood. That includes the search for a vaccine for COVID-19. Just when an alternative to the test seemed to be on the brink of acceptance, the group U.S. Pharmacopeia, which issues quality standards, announced that it still needs more study, a decision that could delay an alternative for years.

“It is crazy making that we are going to rely on a wild animal extract during a global pandemic,” Ryan Phelan, the head of the nonprofit Revive and Restore, told the New York Times. Her group supports a synthetic alternative using genetic technologies.

Declines in horseshoe crabs (Limulus polyphemus) can affect migratory birds that rely on their eggs. The Atlantic population of red knots (Calidris canutus) has fallen due in part to overharvesting of horseshoe crabs for the biomedical industry and commercial fishing bait, making them less resilient to environmental changes.

Unusually cool water temperatures in the Delaware Bay this spring prevented many horseshoe crabs from spawning, resulting in the lowest count of red knots there since counts began. Some 20,000 red knots arrived, but most moved on after they were unable to find food, the Times reports.