In a joint statement with its Japanese partner Takeda, Moderna said the contamination in one of three suspended lots had been traced back to production line flaws at a factory run by its Spanish contractor, ROVI Pharma Industrial Services.
"The rare presence of
stainless steel particles in the Moderna COVID-19 vaccine does not pose an undue risk to
patient safety and it does not adversely affect the benefit/risk profile of the product," the statement said.
Metallic particles of this size injected into a muscle may cause a site reaction, but are unlikely to go beyond that, it added.
"Stainless steel is routinely used in heart valves, joint replacements and metal sutures and staples. As such, it is not expected that injection of the particles identified in these lots in Japan would result in increased medical risk."