Moderna reveals source of COVID-19 vaccine contamination as Japan finds yet another suspect vial

COVID-19 vaccine
Black particles found in a Moderna COVID-19 vaccine vial on Tuesday are believed to be rubber stopper material, according to Japan's health ministry. (Kunal Mahto/iStock/Getty Images Plus/Getty Images)

After yet another contamination report for a Moderna COVID-19 vaccine vial in Japan, the company on Wednesday said its contract manufacturer has identified the probable source of foreign materials.

After investigating, Spain's Rovi Laboratories has concluded that the particulates discovered are stainless steel. The contamination likely resulted from friction between two pieces of metal incorrectly installed in a production line, Moderna said.

Meanwhile on Tuesday in Kanagawa prefecture in Japan, a pharmacist spotted several black particles in a vial. The discovery came after 3,790 shots had been administered from the batch.

Japan’s health ministry said that the contaminant was likely to be rubber stopper material, which also could have entered during the manufacturing process, according to Moderna's distribution partner in the country, Takeda.   

Last week officials suspended three lots of the vaccine—roughly 1.63 million doses—after contaminants were found in one lot of the shots. Over the weekend, more contaminants, but of different material, were discovered from two other Moderna vaccine lots in Okinawa and Gunma prefectures. 

In recent days, two men in Japan, aged 30 and 38, died after receiving their second doses of the Moderna vaccine from the original lot where metallic particles were found. Experts don’t believe the contaminants could have caused the deaths.

“It is unlikely, in my opinion, that contamination of foreign substances led directly to the sudden deaths,” Takahiro Kinoshita, the vice-chair of the Covi-Navi vaccine information group, told Reuters. “If the contaminated substances were dangerous enough to cause death for some people, probably many more people would have suffered from some symptoms after the vaccination.”

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On Wednesday, in a joint statement from Moderna, Takeda and Rovi, the companies said that the grade 316 stainless steel "does not pose an undue risk to patient safety and does not adversely affect the benefit/risk profile of the product."  

The companies said that stainless steel particles of the size discovered may result in a local reaction when injected into a muscle, but no other adverse reactions are likely. Stainless steel is routinely used in heart valves, joint replacements and metal sutures and staples, the companies noted. 

The companies have not received any reports of adverse side effects from those who have received shots from any of the batches where contaminants have been found.

In a regulatory filing last Thursday, Rovi said that the contamination was limited to one product lot bound for Japan. But in the most recent statement, the companies said that the three original lots that were suspended are being recalled.

Contaminants found within the last few days in Kanagawa, Okinawa and Gunma prefectures were from three different lots. Earlier this week, Japan's health ministry said some of the incidents may have been due to needles being incorrectly inserted into vials, breaking off bits of the rubber stopper.

Corrective measures to the manufacturing process have been put into place, the companies said on Wednesday, including improved operating procedures for changeover of manufacturing lines

Last June, Rovi signed on to produce "hundreds of millions" of doses of the Moderna COVID-19 vaccine. In April, the company revealed that it would begin producing bulk drug substance—in addition to bottling doses—from its plant in Grenada, Spain. Previously, the manufacturer received active vaccine ingredient from Switzerland.

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The contamination news comes as Japan is battling a surge of the delta variant, facing approximately 25,000 new cases daily.

The incidents threaten the confidence Moderna had built in its vaccine as it provided more than 200 million doses to 45 countries around the world with virtually no production snafus or quality control or safety issues.