(BLOOMBERG) - Pfizer and BioNTech asked the US Food and Drug Administration to allow their Covid-19 vaccine to be stored for two weeks at temperatures found in normal pharmaceutical freezers, a change that could simplify distribution for the shot.

The partners submitted new data showing stability when the vaccine is stored at minus 25 to minus 15 deg C, they said in a statement on Friday (Feb 19). Current protocol is for storage for up to six months in an ultra-cold freezer at temperatures of minus 80 to minus 60 deg C and shipping in a special thermal container.

"If approved, this new storage option would offer pharmacies and vaccination centres greater flexibility in how they manage their vaccine supply," Pfizer CEO Albert Bourla said.

The partners will keep looking for new formulations to make the vaccine easier to transport and use, BioNTech CEO Ugur Sahin said.

The cold storage necessary for vaccines using messenger RNA technology is one complicating factor for inoculation drives, particularly in countries without the necessary infrastructure.

Vials of the Pfizer-BioNTech vaccine are shipped in a specially designed thermal container, which can be used as a makeshift ultra-cold freezer for as many as 30 days if refilled periodically with dry ice.

Moderna's mRNA vaccine is stable at minus 20 deg C for as long as six months and can be stored at refrigerator temperatures for as many as 30 days.

By contrast, the AstraZeneca vaccine - which uses a different technology - can be stored at refrigerator temperatures for as long as six months.

Before mixing with a saline diluent, the Pfizer-BioNTech vaccine may also be refrigerated for as much as five days at 2 to 8 deg C. The vaccine is administered at room temperature. The partners said they will file the data with other regulators as well in the coming weeks.