The A to Z of Cold Storage and the COVID-19 Vaccine Supply Chain



Mass COVID-19 vaccinations are going on across the world. That has brought forth the need for a cold supply chain to transport the vaccines from the production facilities to the healthcare facilities, preserving the vaccine potency. COVID-19 vaccines, made by Pfizer and Moderna, require freezing temperatures to remain potent. 

While Pfizer’s vaccine needs -70 degree C for effective storage, Moderna’s vaccine needs -20 degrees C. 

The requirement of such ultra-low temperatures (ULT) poses challenges to maintain an effective supply chain for transporting the vaccines.

How to Keep the ULT Supply Chain Intact

In the US and Canada, producers are shipping the vaccines through road and air from the production facilities in Kalamazoo, MI, and the distribution center in Pleasant Prairie, WI. 

For smaller distances, the producers will ship the vaccines directly to the point of use. And for longer distances, they will ship the vaccines to FedEx’s and UPS’ distribution hubs in Memphis, TN, and Louisville, KY, respectively. 

From the distribution centers, there can be one or more stops at intermediate storage facilities. And in some places, like New York, they may even set up regional storage facilities. 

In the distribution channel, the temperature environment has to be within the ULT range. So, the transporters have to use minus 80 freezers for storage and thermal-controlled containers for transporting the vaccine. Both the equipment should have temperature monitors and data loggers to keep track of the temperature stability if the temperature goes out of the prescribed range.

When it comes to healthcare facilities storing the vaccines at the administration point, they need an ultra-low temperature freezer

Such freezers can maintain the temperature at -80 degrees C and also provide long-term storage. The freezers can give a better return on investment as they last around 10 to 15 years. However, there is a downside to these freezers. They consume significant amounts of energy, which means that they will result in generating higher electricity bills.  Transporters use temperature-controlled containers to keep the vaccines during transportation. Typically, such containers have a capacity of 195 vials, equivalent to 1,000 doses, and can be moved around easily. 

They use dry ice to maintain an ultra-low temperature environment during the vaccine transport. But, there are some restrictions with the containers, which should not be opened more than twice a day. While opening, they should be kept open for not more than one minute. And, dry ice must be replaced every five days.

The Challenges of ULT Storage

The necessity of freezing temperatures for effective storage of COVID-19 vaccines poses challenges during widespread vaccine delivery.

Although ultra-low temperature freezers ensure effective storage, the units might not be available in smaller and public health facilities. 

Consider the case of California, where the ultra-low temperature storage capacity in local health departments is limited. 

Even the Centers for Disease Control and Prevention (CDC) has recently advised jurisdictions not to purchase such units at this time. 

Due to the unavailability of an adequate number of ultra-low temperature freezers in the last mile of the cold supply chain, vaccine transporters use temperature-controlled containers. Due to their limitations, adequate care has to be taken while opening the containers. They should not be kept open for long.

Also, the vaccines should be administered as quickly as possible to ensure they do not lose potency. So, healthcare service providers should ensure that they line patients before they start administering the vaccines. 

Ultra-low temperature freezers can store Pfizer’s vaccine for up to six months. But temperature-controlled containers can store the vaccine effectively up to a maximum of 30 days.

After that, vials can be thawed and stored in refrigerators at 2 to 8°C for up to five days. Keep in mind that once you thaw the vaccines, you cannot freeze them again. 

Healthcare facilities can have a total of 35 days to use the vaccine without using ultra-low temperature freezers. 

The CDC recommends that the vaccines should be kept in the coolers for a maximum of 15 days and refrigerators for up to five days, reducing the time frame to 20 days for healthcare facilities without ultra-low temperature freezers. 

Notably, the stringent freezing temperature requirements are unique to Pfizer’s vaccine. But Moderna’s vaccine needs a storage temperature of -20 degrees C, which is above the ultra-low range. And the vaccine can remain stable within 2 to 8 degrees C for 30 days. Moreover, it can also remain stable at room temperature for up to 12 hours. Therefore, Moderna’s vaccine suits better for smaller rural towns with an ultra-low temperature storage facility.

The phase three vaccines are likely to be distributed in the US soon and do not require ultra-low temperature environments. The vaccines are:

AZD1222 by AstraZeneca – requires normal refrigerated conditions of 2 to 8 degrees C for storage.

NVX-CoV2373 by Novavax – need a temperature range of 2 to 8 degrees C. It can be distributed in unfrozen, liquid formulations.

Ad26.COV2.S by Johnson & Johnson – can remain stable for two years at -20 degrees C., And its stability can extend by more than three months in the 2 to 8 degrees C range.

In the days to come, you can expect the uses of 2 to 8 degrees C to increase significantly in the COVID-19 cold supply chain. It will help healthcare facilities store the vaccines for a longer time, which will also help reduce wastage. The World Health Organization estimates a vaccine wastage of 50 percent worldwide due to improper storage. 

However, COVID-19 vaccines, when stored in 2 to 8 degrees C fridges, will call for strict temperature monitoring to ensure vaccine stability as there will be fewer fluctuations. With the continuation of mass COVID-19 vaccinations and the emergence of the new vaccines, the role of ultra-low temperature freezers in the cold supply chain will become less important. However, the importance will not go away totally. 

Mila Jones
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