TOKYO—Japan's health ministry said Thursday foreign materials were found in some portions of unused doses of Moderna Inc.'s COVID-19 vaccine and the use of around 1.63 million doses manufactured in the same production line has been suspended as a precaution.
Japanese drugmaker Takeda Pharmaceutical Co., which is in charge of sales and distribution of the vaccine in the country, said it has yet to see any reports of safety issues. Some of the 1.63 million doses distributed to 863 vaccination centers have already been used.
"To date, no safety or efficacy issues have been identified," Moderna told Kyodo News, adding it is "carefully assessing this matter and at this point does not have further comments on root causes."
The health ministry said the 1.63 million doses of Moderna vaccine were produced in the same production line at the same time in Spain, and fall under 3 lot numbers -- 3004667, 3004734 and 3004956.
The ministry said it believes the risk of safety issues is "not significant," but will ask each facility that received the doses not to use them.
It revealed the lot numbers so that concerned individuals can check whether they may have received a potentially contaminated shot before the affected vaccine doses were suspended.
The size of foreign substances confirmed in 39 vials is believed to be a few millimeters, with their elements being unknown. Moderna is conducting an investigation into the materials, according to the ministry and Takeda.
The Ministry of Health, Labor and Welfare said foreign substances have been confirmed since Aug. 16 at 8 vaccination sites in the prefectures of Ibaraki, Saitama, Tokyo, Gifu and Aichi. Takeda reported them to the ministry on Wednesday.
Takeda has requested an emergency probe by the US biotechnology firm, while urging medical institutions and other entities not to use any doses of the vaccine showing abnormality, even for doses not subject to the suspension.
The Japanese company added it will make efforts to prevent the suspension from affecting the availability of coronavirus vaccine doses in the country.
On similar abnormalities that may have been found in other countries, Moderna said, "On an ongoing basis, Moderna monitors and expeditiously assesses questions we receive about our products from global markets."
"Local authorities will make their own decisions about disclosure of information following these assessments," the company said.
The problem came to light at a time when Japan is struggling to contain a spike in coronavirus infections, with the government announcing a plan Wednesday to place 8 more prefectures under its COVID-19 state of emergency.
While vaccinations against COVID-19 are under way in Japan, the highly contagious Delta variant of the coronavirus has sent daily reported cases surging in many parts of the country.
Over 10 million doses have already been used in the country since the Moderna vaccine was approved for emergency use in May, according to the government.
The Japanese government signed a contract with Moderna to receive 50 million doses of the COVID-19 vaccine by the end of September. Currently people aged 12 and over can receive shots of the vaccine.
The vaccine, like the one developed by US pharmaceutical firm Pfizer Inc. and its German partner BioNTech SE, uses a new technology called messenger RNA, or mRNA, and is administered in 2 doses given 4 weeks apart.