Pfizer’s vaccine, which was the first shot to be approved to prevent COVID-19 in the United States, was previously thought to need ultra-cold freezers to keep the vaccine between 112 degrees below zero and 76 degrees below zero. Now, the FDA says that as long as the vials are still frozen, they may be kept intact at “conventional temperatures commonly found in pharmaceutical freezers.”
Once thawed and diluted, the vaccine has the same shelf life of five days before degradation makes it ineffective.
Cold vs. Ultra-Cold
The differentiation between cold and ultra-cold freezers was a severe limitation of the Pfizer vaccine, since in many rural areas, ultra-cold freezers are few and far between. And it’s difficult to transport the vaccine to these rural areas while keeping it extremely cold.
According to Paul Kamitsuka, MD—an infectious disease physician at Wilmington Health, Chief Epidemiologist at New Hanover Regional Medical Center, and partner with the Roll Up Your Sleeves initiative—Pfizer and the FDA were erring on the side of caution by requiring the vaccine to be stored in such a frigid environment.
“While mRNA technology isn’t new, this is the first instance of widespread use. Pfizer had thought that you needed extremely cold temperatures to keep the fragile mRNA, which is embedded within a fatty envelope, stable,” Kamitsuka tells Verywell.
Since the Moderna vaccine uses the same mRNA technology but doesn’t require a deep freeze, there were questions about whether it was necessary for Pfizer. Asha Shah, MD, MS, associate director of infectious diseases at Stamford Health, explains that Pfizer, which was first on the scene, wanted to guarantee that higher temperatures wouldn’t damage the vaccine.
“I think it’s important to be as conservative as possible to maintain the integrity of the vaccine,” she tells Verywell. “As with anything with the vaccine, as we do more, we learn more. That’s why it took time to come out with this information.”
Rural Areas Will See the Most Impact
According to Shah, not much will change at large vaccination sites, since most were already using ultra-cold storage. But at more rural sites—or any site without a special freezer—this change means that if there is more Pfizer vaccine supply available than Moderna or Johnson & Johnson at a particular time, they can actually accept it. Until now, smaller vaccination sites without suitable equipment may have had to turn away vaccines that they couldn’t store properly, becoming blockers to the vaccine rollout.
Shah says that depending on guidance in each state or county, all vaccines may have to be used before new doses are sent. If pharmacies and other vaccination sites are able to use their entire supply with minimal waste and quickly receive new doses, the U.S. will get closer to the goal of inoculating 300 million adults by the end of May.
“The more vaccines we get in arms, the faster we’re going to work our way out of this pandemic,” Kamitsuka says.
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