The Pfizer and BioNTech COVID-19 vaccine was authorised on Wednesday to be stored at standard freezer temperatures for up to a month.
The U.S Food and Drug Administration said the approval should make the vaccine more widely available.
Unopened, thawed vials of the vaccine were previously only able to be stored for a maximum of 5 days.
Now, they can be stored in a refrigerator at 2 to 8 degrees Celsius for 31 days.
The change is an important one for global and remote U.S facilities..
that have poor transport and storage infrastructure.
Canada has made a similar move to relax the refrigerator requirements for the Pfizer/ BioNTech vaccine.
The vaccine was granted emergency use authorization in the U.S. and Canada last December.
This month, both countries approved the use of the vaccine on children as young as 12.