Japan suspended use of about 1.63 million doses of Moderna vaccine after contamination was found in unused vials, raising concern of a supply shortage as the country tries to accelerate vaccinations amid a Covid-19 surge, Reuters reports.

The health ministry said contamination was reported from multiple vaccination sites. Some doses might have been administered, but no adverse health effects have been reported so far, officials said.

Takeda Pharmaceutical Co, a Japanese drugmaker in charge of sales and distribution of the vaccine in Japan, said it decided to suspend use of doses manufactured in the same production line as a safety precaution.

It asked Moderna to conduct an emergency investigation and told medical institutions and organisers to stop using the vaccine produced in Spain and shared the production numbers that may be affected.