Why Does Pfizer's COVID-19 Vaccine Need To Be Kept Colder Than Antarctica?

Two drugmakers, Pfizer and Moderna, have announced promising interim results for their vaccine candidates, raising hopes in the U.S. and abroad that the end of the pandemic may be in sight. But, if and when the vaccines are authorized by the Food and Drug Administration, distributing them presents a daunting challenge.

One big reason? One of the front-runners in the vaccine race — the one made by Pfizer — needs to be kept extremely cold: minus 70 degrees Celsius, which is colder than winter in Antarctica. Moderna has said that its vaccine needs to be frozen too, but only at minus 20 Celsius, more like a regular freezer.

Since there will be limited vaccine doses at first, immunization managers across the country will need to have plans to distribute any and all vaccine doses that are available. For months, they've been puzzling over the particular challenges presented by the Pfizer vaccine, which requires these ultra-cold conditions.

"I believe it can be done," says Debra Kristensen, a 30-year veteran of vaccine innovation and supply chains at PATH, an international nonprofit focused on public health. "Ebola vaccine, for example, was successfully used in a few African countries and also required this ultra-cold chain storage."