TORONTO -- Health Canada has updated their requirements for the transportation of the Pfizer-BioNTech COVID-19 vaccine, reporting that the vaccine can be transported while thawed, but only for a short period of time.

In a letter to health-care professionals that was posted on Monday, Health Canada stated that they have received new data from Pfizer that supports new options for transportation and storage.

Among the new guidance is the news that undiluted vials can be transported in a thawed state at 2 to 8 C for up to 12 hours.

Although it was previously known that thawed vials could be kept refrigerated for up to five days, or 120 hours, previous guidance specified that the vaccine had to be transported in a frozen state.

If the vials are being transported and then stored at 2 to 8 C, the 12 hours of transport count as part of the 120 hours of storage, according to the new guidelines.

This follows the revelation last week that the Pfizer vaccine can be stored or transported in frozen vials at -25 C to -15 C for up to two weeks, temperatures that are achievable by ordinary commercial freezers.

“The review of data provided by Pfizer-BioNTech confirms the maintenance of the vaccine quality under these new storage and transportation conditions,” the letter stated.

Vials that have been transported at -25 to -15 C can be taken back down to the recommended storage condition of -80 to -60 C, but only once. They cannot be taken to a warmer temperature and then brought back down multiple times.

When the Pfizer-BioNTech vaccine was first approved, one of the big challenges for the vaccine rollout was the strict requirements for what temperature the vaccine has to be stored at. Initially, the vaccine was meant to be transported only at -80 to -60 C, which meant the need for special vehicles and other transportation that could create those colder-than-Antarctica conditions.

Since then, the company has been performing more tests to ensure the vaccine does not lose its effectiveness if transported at other temperatures.

This news could make it easier to get the vaccine up to more remote communities that may not have the ultra-cold freezers needed to store the vaccine at the recommended -70 C.