Moderna probes reports of COVID-19 vaccine contamination in Japan

It's been a relatively smooth ride for Moderna's global COVID-19 vaccine roll out. But on Wednesday, the company said it's investigating the possible contamination of one batch sent to Japan. 

The company has received "several complains of particulate matter" in vials of its vaccine, a Moderna spokesperson said over email.

The complaints came from "one product lot" which was distributed in Japan, the representative added. Kyodo News reported that Moderna's vaccine partner in Japan, Takeda, has suspended the use of 1.63 million doses.

Moderna said it believes an issue affecting a production line at a contract manufacturing facility in Spain is responsible.

Last June, Spanish CDMO Rovi signed up 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.

Also in April, Rovi announced that it was upgrading its plant to double its capacity to produce Moderna's vaccine.

RELATED: Moderna inks fill-finish pact with Spain's Rovi for 'hundreds of millions' of COVID-19 shot doses

So far, Moderna says, it has not identified any safety concerns with the lot of contaminated vaccines. Moderna has put the lot and two additional "adjacent lots" on hold.

Moderna is "proactively communicating with Japan's health authorities and its partners as the investigation proceeds," the company said. The company "remains committed to working transparently and expeditiously with its partner, Takeda, and regulators to address any potential concerns."

RELATED: What does it take to supply COVID-19 vaccines across the globe? Here's how the leading players are working it

While Johnson & Johnson and AstraZeneca have had high-profile production problems with their COVID-19 vaccines, it's been a relatively smooth ride so far for Moderna and the other leading COVID vaccine from Pfizer-BioNTech.