Japan's health ministry has allowed the Pfizer-BioNTech coronavirus vaccine to be transported and stored at temperatures commonly found in pharmaceutical freezers.
The ministry gave the green light on Monday, after examining data from the US pharmaceutical giant.
Pfizer had asked that the vaccine -- which was authorized for use in February -- be kept at around minus 75 degrees Celsius in special freezers for long-term storage.
The ministry had authorized the use of cool bags when doses are being transported to clinics. But experts warned that, if unfrozen vials of the vaccine are subjected to vibrations their quality and efficacy could be affected.
Pfizer now says the vaccine remains stable for a period of up to two weeks even when it is stored at minus 15 to minus 25 degrees Celsius.
The ministry plans to circulate the Pfizer data among municipalities in Japan, which will, in turn, allow them to use delivery companies' refrigerated vehicles to transport the vaccine.
Last Thursday, the US Food and Drug Administration loosened rules for the Pfizer vaccine to allow its vials to be transported and stored at conventional temperatures commonly found in pharmaceutical freezers.