The two major U.S. developers of the early Covid-19 vaccines are Pfizer/BioNTech and Moderna. They both developed mRNA vaccines, a relatively new type of vaccine. A major supply-chain issue is the temperature requirement for these vaccines.

The Pfizer vaccine needs to be stored at between –112° F (–80° C) and –94° F (–70° C), and the Moderna vaccine needs temperatures around –4° F (–20° C), which is close to the temperature of commercial-grade freezers. A third company developing vaccines, AstraZeneca, says it needs regular refrigeration temperature of 36° F to 46° F, or 2° to 8° C.

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