When Pfizer-BioNTech’s vaccine became the first authorized for use in the U.S., the good news came with a catch: the vaccine, the first of its kind using a new mRNA-based technology, needs to be stored at ultra-cold temperatures (-80°C to -60°C) until thawing just before being injected into people’s arms. State health centers, hospitals and other potential vaccination sites scrambled to acquire special freezers that could reach these deep-freeze temperatures, and Pfizer developed a special shipping container that could keep doses appropriately chilled for up to a month as long as the container was continuously supplied with dry ice.