Five weeks after Japan suspended the use of three lots of the Moderna COVID-19 vaccine, the company and its Japanese distributor Takeda have concluded (PDF) that “human error” caused the presence of metallic particles in vials.
The errors occurred at a Rovi manufacturing plant in Spain, which released three vaccine lots after a fourth lot from the same production series failed an inspection. The fourth and fifth lots from the series were held back, Moderna explained in the 16-page report.
Rovi made Moderna aware of the foreign matter when it was discovered. But Rovi incorrectly attributed the contamination to a “vial breakage event,” which happened after the first three lots had been completed.
Contaminants, identified by an independent lab as 316L stainless steel—the type commonly used in pharmaceutical and food manufacturing—were caused by friction between two pieces of metal that were incorrectly installed in the stopper module of the production line.
The mistake occurred at the changeover of the line by a plant mechanic before the manufacture of the first lot of the series. The incorrect assembly was “due to human error specific to visually misjudging the precise 1 mm gap between the star-wheel and the stopper,” the report said.
Corrective measures to prevent a reoccurrence include a new precision tool and improved standard operating procedures at the changeover.
The investigation began in late July when particles were discovered in vials from one vaccine lot in Japan. Health officials halted distribution from the lot and two others, deactivating a total of 1.63 million vaccines.
Over the next two weeks, three people who had received shots from the second lot died, including two men in their 30s. No link has been established. The investigation of the deaths is ongoing, said the report. Moderna and Takeda have concluded that the presence of stainless steel particles does not pose any undue risk to patient safety.