Investigation reveals contaminant in Moderna vaccines

Sept. 1, 2021

The health ministry in Japan has revealed the source of the visible particles recently found in Moderna vaccines.

According to the results of an investigation by Moderna and Japanese distributor Takeda Pharmaceuticals, the particles were stainless steel. In a statement, Takeda said that the contamination was most likely caused by friction that occurred between two pieces of metal on the machine used to stopper the vaccines.

The companies added that the contamination is not expected to pose a health risk.

"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," the companies said in a joint statement.

After the contamination was initially reported, Japan halted the use of about 1.63 million doses of the Moderna vaccine as a precaution. The health ministry is also still investigating the deaths of two men — both in their 30s — who recently died shortly after getting their second doses of the Moderna vaccine, both from this recalled lots. So far, Takeda said, there is no reason to suspect that the vaccine was the cause of the deaths.