By JOHN RICHARD SCHROCK
Super-cold refrigeration is a new concept to citizens not involved in molecular biology research. It is a requirement of the Pfizer vaccine that has just provided preliminary indication that it might be 90 percent effective. If further research supports this early data, this vaccine could be approved and begin to become available in the next two months. But this vaccine must be kept at a super low temperature and transported in a “cold chain.” Why?
Chemical reactions generally increase with temperature. Therefore, to slow down spoilage—a chemical reaction—we place food molecules in a refrigerator where they remain cooler and chemical reactions are slower. Milk that would spoil in a day now lasts a week in a refrigerator, but still eventually spoils. Kitchen refrigerators operate at between 35° F and 38° F (1.7° to 3.3°C). Our kitchen freezer temperatures are generally around -1° F (-18° C). But molecular interactions still continue to slowly occur and, in the case of this RNA vaccine, it spoils rapidly at these temperatures.
Biology has long required ultra-cold freezers in order to store DNA, RNA, proteins, cell extracts, and other complex reagents. When prospective parents have sperm or eggs frozen for future use, it requires storage in liquid nitrogen at -320.8 °F (-196 °C)! The Pfizer vaccine is an RNA vaccine and needs to be stored in standard ultra-cold freezers often called “minus 80" or “negative 80” freezers indicating their moderately low temperature of -80° to -86 °C (-112° to -123 °F).
University and research facilities commonly house ultra-cold units because masters and doctoral students working with DNA, RNA and other biochemicals must keep these expensive molecules from breaking down during their research.
A few years ago, I found myself in the biology office at a time the lights went off. Usually it only takes a minute for power to re-route around a downed power line and come back on again. It didn’t. We called for the university electrician to bring generators as soon as possible. We had large upright ultra-colds and smaller desktop ultra-colds, all holding expensive and valuable biological chemicals that must remain near -80° C. Without electricity to drive the cooling coils, they would gradually warm and these research chemicals would begin to break down by -60° C. Our smaller units lacked insulation to hold the cold more than a half hour. Expensive research materials would be lost. Students could have to work another year longer. Portable generators kept the ultra-colds working. Today, we have back-up generators that automatically cut in during a power loss. That is how sensitive biomolecules can be. And that is why an RNA vaccine must remain ultra-cold.
So will all of the vaccination sites around the United States and world that may use the Pfizer vaccine need to have ultra-cold units? They are not cheap. And they are energy hogs and expensive to operate.
According to a CNN report, North Dakota bought 13 ultra-low temperature freezers for $100,000 according to a spokesperson for their state health department. But that goes against the CDC recommendation to not purchase ultra-colds. Instead, the CDC is recommending “thermal shippers,” insulated containers that use dry ice (frozen carbon dioxide at -78.5° C (-109.3° F)). CNN reported that North Dakota bought its own dry ice machine for $48,000 and paid nearly the same amount for a three month supply of liquid carbon dioxide that makes dry ice.
Maintaining the “cold chain” from vaccine production point to vaccination site is critical. With dry ice replenished, the vaccines can remain in their thermal shippers for no more than 15 days. That insulated box can only be opened twice per day and for no more than one minute, according to Pfizer’s instructions. The ultra cold Pfizer vaccines would thaw if exposed to open air at room temperature for five minutes. Therefore the vials, containing five doses each, are placed into a standard refrigerator where they will not last beyond five days. When the five shots are extracted from each vial, they must be injected within six hours. Every patient must then receive a second booster shot three weeks later.
The Salk polio vaccine was an attenuated (broken) virus that did not require a cold chain. Many other vaccines in current trials are similar and can reach third world populations that cannot support this cold chain. We will know next year if the United States can accomplish this ultra-cold logistics.
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John Richard Schrock has trained biology teachers for more than 30 years in Kansas. He also has lectured at 27 universities in 20 trips to China. He holds the distinction of “Faculty Emeritus” at Emporia State University.