How Cold is Cold Enough for a Vaccine?

Two new vaccine therapies are on the horizon for COVID-19. Both need to be stored at temperatures cold enough to harden ice cream into a block of ice that only specialized freezers can produce.

The cold storage requirements that you’ve heard about are raising serious questions. Why do they have to be kept so cold? It’s all in the RNA, Messenger Ribonucleic Acid (mRNA) to be exact. mRNA is usually used by the body as a go-between—telling cells which protein to start producing. The mRNA in these vaccines tells the cells in your body to produce the ‘spike’ protein, which can be found on the outside of the virus particle. In fact, the ‘spike’ protein is part of the crown that the virus is named after (corona is Latin for crown). This method of vaccination has been shown to be highly effective. Some good news about this method is that it does not require production in chicken eggs. The not-so-good news is that it’s hard to get to patients because naked RNA breaks down rather quickly if it’s not stored properly.
To understand how this degradation of RNA happens so quickly, you have to dust off your old biology book. Biology’s central dogma states, “DNA leads to RNA, and RNA leads to proteins.” DNA in a cell is supposed to stay around for a long time, but the RNA that is created as a messenger to help in the process of making the protein (mRNA) is digested so that new messages can be sent.  
Now we know how it happens, but why does RNA need to be digested or degraded? Let us use a voicemail message analogy. What if your phone kept every message that you ever received? Very quickly, the old messages would stack up, and there might be trouble processing new messages. Cells contain organelles that read the message, process the message (create a protein), and finally recycle the message into individual RNA molecules that are used to create a new message. 
The mRNA in both new vaccines are kept in a lipid bubble, similar to the plasma membrane of a cell. Depending on the makeup of the lipid bubble, you might need to refrigerate at -80 degrees C or at -20 degrees C.
Extreme cold temperatures can slow down most degradation processes, especially in RNA. Just like storing food in a freezer keeps it from going bad, storing vaccines made from fragile mRNA in a freezer achieves the same thing. 

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