On Thursday, August 26, Japan announced that it had stopped distributing 1.63 million Moderna COVID-19 vaccine doses over reports of possible contamination. 

On August 16, the health ministry reported a batch of nearly 560,000 vials had some doses with impurities. The Japanese government received notice of the issue this Wednesday.

According to the Japan Times newspaper, contamination was also reported from seven other vaccination centers, with 39 vials or 390 doses found with impurities.

Japan Times added that the health ministry has made the batch numbers public so that anyone who received the shots before the ban can check if theirs was one of the tainted doses.

Moderna told Reuters the contamination might stem from the factory in Spain. 

Takeda Pharmaceutical, the company in charge of vaccine distribution in the country, although did not reveal precisely what the “foreign objects” were in the vaccines batch, said it was particulate matter, BBC noted.

Rovi, a Spanish pharma firm, which takes charge of bottling and finishes Moderna vaccines for distributions outside of the U.S., said it was checking for contamination in other batches but believed that the issue might only affect Japan.

Although no safety or efficacy problem related to the doses had been reported, the batch suspected of contamination had been rolled out in the western prefecture between August 6 and August 20, Reuters said. 

Japan’s defense ministry revealed there were 565,400 doses in the lot but was not specific in the number of recipients who might have received them.

ANA, a Japanese carrier, updated the outlet that roughly 4,700 doses from the affected Moderna lot had been used and that all vaccines scheduled for Thursday would be canceled.

Japan Airlines had also canceled some COVID-19 immunizations for its employees after receiving Moderna vaccines that contained particulate matter on Thursday.

Japan had only started to distribute COVID-19 vaccines by Moderna in May, BBC said. Aside from it, Pfizer and AstraZeneca are also being administered in the country. According to the news media, over 40% of Japanese people are fully immunized, with about 50% receiving only one shot.