The complexity of the supply chain has some questioning whether a coronavirus vaccine could be produced quickly at the scale needed.

A vaccine supply chain involves a long list of ingredients, including some that seem odd, such as a derivative of horseshoe crab blood called “limulus amebocyte lysate,” or LAL, and a substance extracted from shark liver oil known as squalene. And a COVID-19 vaccine might also contain messenger ribonucleic acid, or mRNA.