On Feb. 25, 2021, the U.S. Food and Drug Administration announced that it was allowing undiluted frozen vials of the Pfizer-BioNTech COVID-19 Vaccine to be transported and stored at conventional temperatures commonly found in pharmaceutical freezers for a period of up to two weeks.

This reflected an alternative to the preferred storage of the undiluted vials in an ultra-low temperature freezer between -80 C to -60 C (-112 F to -76 F).

Pfizer submitted data to the FDA to demonstrate that their COVID-19 vaccine remains stable after storage of the undiluted vials for up to two weeks at standard freezer temperature. The alternative temperature for storage of frozen vials is not applicable to the storage of thawed vials before dilution (which can be held in the refrigerator for up to 5 days), or on the storage of thawed vials after dilution (which can be held at refrigerator temperature or room temperature for use within 6 hours).