If One Leading Covid Vaccine Works, Thank This Tiny Firm in Rural Austria

VIENNA—A key ingredient in what could be the first U.S.-approved Covid-19 vaccine comes from a family-owned company with 90 employees in the Austrian countryside, underscoring the fragility of the potential treatment’s supply chain.

Polymun Scientific Immunbiologische Forschung GmbH is one of a handful of makers of lipid nanoparticles, microscopic vessels used to deliver genetic material into the body.

For…