The Food and Drug Administration (FDA) is allowing undiluted frozen vials of the Pfizer-BioNTech coronavirus disease 2019 (COVID-19) vaccine, BNT162b2, to be transported and stored at -25°C to -15°C (-13°F to 5°F), temperatures commonly found in pharmaceutical freezers, for a period of up to 2 weeks. 

The update is based on recently submitted data that demonstrated the stability of the undiluted vaccine vials for up to 2 weeks at standard freezer temperatures. Previously, the labeling stated that undiluted vials had to be stored in an ultra-low temperature freezer between -80ºC to -60ºC (-112ºF to -76ºF). 

According to the updated vaccine fact sheet, any hours used for transport at -25°C to -15°C (-13°F to 5°F) count against the 2-week limit for storage at -25°C to -15°C (-13°F to 5°F). Frozen vials stored at -25°C to -15°C (-13°F to 5°F) for up to 2 weeks may be returned 1 time to the recommended storage condition of -80ºC to -60ºC (-112ºF to -76ºF). Total cumulative time the frozen vials are stored at -25°C to -15°C (-13°F to 5°F) should be tracked and should not exceed 2 weeks.

“The alternative temperature for transportation and storage will help ease the burden of procuring ultra-low cold storage equipment for vaccination sites and should help to get vaccine to more sites,” said Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research.

Additionally, Pfizer and BioNTech have initiated a study to evaluate the safety and immunogenicity of a third dose of BNT162b2 against COVID-19 caused by newly emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants. The study will assess up to 144 participants from the phase 1 study in the United States in 2 age cohorts, 18 to 55 and 65 to 85 years of age. A 30µg booster dose of the current vaccine will be administered 6 to 12 months after the initial 2-dose regimen.

Participants will be assessed when the third dose is administered followed by 1 week and 1 month after, and for up to 2 years. Sera from these participants will be evaluated to see if vaccination produces neutralizing titers against the variants of interest.

“While we have not seen any evidence that the circulating variants result in a loss of protection provided by our vaccine, we are taking multiple steps to act decisively and be ready in case a strain becomes resistant to the protection afforded by the vaccine. This booster study is critical to understanding the safety of a third dose and immunity against circulating strains,” said Albert Bourla, Chairman and CEO, Pfizer. 

In addition to the booster study, the Companies are in ongoing discussions with regulatory authorities regarding a registration-enabling clinical study to evaluate a variant-specific vaccine with a modified mRNA sequence. A new version of the Pfizer-BioNTech vaccine would be used in the study based on the B.1.351 lineage identified in South Africa.

In December 2020, BNT162b2 was granted Emergency Use Authorization by the FDA for active immunization to prevent COVID-19 in individuals 16 years of age and older. The vaccine is administered intramuscularly as a 2-dose series (0.3mL each) spaced 21 days apart.


  1. Coronavirus (COVID-19) update: FDA allows more flexible storage, transportation conditions for Pfizer-BioNTech COVID-19 vaccine. [press release]. Silver Springs, MD: US Food and Drug Administration; February 25, 2021.
  2. Pfizer and BioNTech initiate a study as part of broad development plan to evaluate COVID-19 booster and new vaccine variants. [press release]. New York, NY and Mainz, Germany: Pfizer Inc. and BioNTech SE; February 25, 2021.