Human errors at a manufacturing plant forced Johnson & Johnson to throw out 15 million doses of its COVID-19 vaccine – enough to vaccinate 7% of the U.S. adult population. The New York Times, which first reported the loss on March 31, 2021, called it “a major embarrassment” for the vaccine-maker and its subcontractor, Emergent BioSolutions. But while errors with an impact of that magnitude sound shocking, they’re also a reminder that the U.S. vaccine manufacturing process has strict quality control measures designed to catch these problems before they reach the public. Vaccine manufacturing is complex, with many potential points...