An ultracold storage facility capable of storing more than 1.6 million doses of COVID-19 vaccine has been completed at the University of Arizona.

The so-called "freezer farm" includes eight storage freezers to accommodate the first vaccines expected to be available in the U.S. – the Pfizer vaccine, which received emergency use authorization from the Food and Drug Administration on on Dec. 11, and another candidate produced by Moderna. Seven of the freezers are ultracold freezers that operate at minus 80 degrees Celsius (minus 112 degrees Fahrenheit), and the other one can provide storage at minus 20 C (minus 4 F). Two additional minus 20 C freezers are on the way.

With the first shipments of vaccine expected in mid-December, the UArizona freezer farm could play an important role in Arizona's plan for vaccine distribution, with the ability to serve as a secure, reliable and state-of-the-art facility where the vaccine can be held and readied for distribution through medical providers.

"This freezer farm plugs directly into the existing infrastructure of a long-standing, proven relationship between basic science and clinical research," said University of Arizona President Robert C. Robbins. "By providing this facility, we are continuing to do what we have been doing throughout this pandemic – leveraging the unparalleled, diverse and creative strengths we have at this university to serve our community and distribute aid whenever possible."

Each freezer at the facility has the capacity to hold between 100,000 and 187,000 doses of vaccine, said David T. Harris, a professor in the UArizona Department of Immunobiology and executive director of the University of Arizona Health Sciences Biorepository.

"The University of Arizona is poised to be instrumental in receiving, managing and distributing COVID-19 vaccine," Harris said. He added that the biorepository is naturally positioned to take this role.

"For the past five years, we have been involved with banking biological specimens from the hospital and university researchers," said Harris, who is also a member of university's BIO5 Institute. "We have been involved in research with ICU and COVID patients, as well as with producing the PCR tests and tens of thousands of rapid antigen tests. We know exactly how to work in that environment."

Unlike more traditional vaccines that are based on proteins, the Pfizer and Moderna COVID-19 vaccines are built on messenger RNA, a single-stranded biological molecule that is ubiquitous in all living cells and functions as a blueprint for cellular machinery that translates genetic information into proteins. Because mRNA is much less stable than a protein, it must remain frozen in order to maintain its structural integrity and functionality.

The Pfizer vaccine requires storage at minus 70 C to remain effective. Moderna's product also has to be kept frozen, but the company says minus 20 C is sufficient. The different requirements are expected to impact how vaccines will be distributed. While specialized facilities are necessary to provide ultracold storage for the Pfizer vaccine, the Moderna vaccine can be stored in freezers that are commonly found at health care provider offices and pharmacies.

According to Pfizer, its vaccine can last up to six months under ultracold storage conditions. During transit, the vaccine vials will be kept on dry ice in specialty shipping boxes that can be refreshed with dry ice every five days for up to 15 days. Dry ice is frozen and compressed carbon dioxide and exists at minus 78.5 C (109.3 F).

"It may sound like it's a really difficult situation, but universities and laboratories have been shipping stuff on dry ice around the world for the past 30 years," Harris said. "Dry ice is not anything new and not something that is in short supply."

Each freezer at the UArizona freezer farm will be closely monitored by trained personnel, and several tanks of liquid nitrogen are on hand to help maintain safe freezing conditions in case of technical issues or power outages. The secure facility has restricted access and is monitored 24/7 to prevent unauthorized entry. For added security, no individual is able to access the facility alone.

The UArizona freezer farm is an important piece in an infrastructure of cold storage facilities that will serve as hubs in the state's distribution network, said Crystal Rambaud, vaccine-preventable disease manager with the Pima County Health Department.

UArizona Assistant Vice President for Facilities Management Chris Kopach, who serves as incident commander for the university's Incident Command System, praised the ICS team, which includes representatives from the university and the broader community, for its work to make the freezer farm a reality.

"I'm very proud our team in looking ahead in a forward manner to address a major need in establishing the freezer farm to house the vaccine and provide collaborative support for our county," he said. "The ability to provide storage and distribution will provide benefits to all of Pima County."