Meeting the challenges of rapid Covid-19 vaccine cold chain deployment

Ultralow temperatures require a revision of vaccine distribution technology

For months, pharmaceutical organizations and researchers worldwide have been focused on developing a vaccine for Covid-19. “Operation Warp Speed” (OWS), a collaboration among several U.S. governmental departments and 18 biopharmaceutical companies, was created to accelerate the development of a Covid-19 vaccine.

Upon vaccine approval, OWS will aim to deliver 300 million doses by January 2021. This is an unprecedented and complicated challenge, given the speed of deployment, global scale of distribution, and because some vaccine candidates must be stored at ultra-low temperatures (ULT), which are beyond the normal cold storage range for vaccines (-40°C to -4°C).

Although OWS accelerated vaccine development/testing, meeting the cold chain storage requirements of a vaccine could prove the project’s most daunting challenge.

Today, few vaccine manufacturers, third-party logistics (3PL) providers, healthcare systems or pharmacies are set up to continuously store and transport vaccines in temperatures as low as -80°C. Therefore, to meet this monumental task, these organizations must rapidly ramp up ULT cold chain capacity—from end to end—to safely store and deliver vaccines to hundreds of millions of people.

There is a lot at stake. The World Health Organization estimates that more than 50% of vaccines lose their efficacy globally every year due to the lack of proper temperature control, logistics or shipment-related issues. Given the urgent global need for a Covid-19 vaccine, this is not an option. By proactively addressing key challenges, manufacturers, regional 3PLs and local points of patient care can rapidly deploy the ULT freezers needed to maintain vaccine efficacy while mitigating potentially negative financial and infrastructural impacts to their organizations.

Challenge: Be prepared for the range of temperatures at which multiple Covid-19 vaccine candidates may have to be stored

There are currently more than 30 vaccines in the testing pipeline worldwide, so it’s not yet possible to tell at which temperatures an approved vaccine will need to be stored. It already appears that certain candidates will require -80°C storage, while others may only require -50°C to -40°C and warmer storage. Not being able to meet the storage requirements of any one of the viable vaccine candidates could put all cold chain stakeholders at a disadvantage. The smart play is to cover all the bases now, so that they will be ready the moment vaccine approval arrives.

Solution: Choose ULT freezers with the widest temperature range to optimize cold storage setpoints for most/all vaccine candidates

Look for ULTs that can maintain the broadest range of temperature setpoints (from -86°C to -20°C), not a limited range starting below -50°C. By opting for a ULT freezer that supports a wider range of temperatures, facilities can accommodate the storage efficacy requirements of more vaccine candidates, regardless of which are ultimately approved.

Challenge: Overcome facility infrastructure obstacles when quickly ramping up ULT freezer capacity

Few distribution center facilities are designed to house high-volume biobanking operations. As 3PLs and pharma distributors find themselves rapidly adding ULT freezer capacity, they can expect to encounter infrastructure challenges, including heat generation, limited floor space, power demands and high energy costs.

Equipment options

Generally speaking, there are three available choices for ultra low-temperature storage: continuous replenishment of dry ice (CO2) or liquid-nitrogen (LN2) units; conventional compressor-powered freezers, and the free piston Stirling engine units offered by Stirling Ultracold.

Deploying CO2 or LN2 units in regions or locations where those commodities are readily available has been the solution for years; typically, they are not shipped long distances. However, the risks associated with handling, the negative impact on the environment and lack of control over individual vial temperature has pushed the industry to find better solutions. Freezers came into play as technology advanced, but freezer operation depends on continuous power availability and reliable monitoring and plenty of space to work with a number of recent events where freezers failed (and precious biobanked materials were lost forever) because of monitoring or maintenance upsets.

Conventional compressor-driven units have the advantage of being familiar to HVAC and other facility engineers—the technology is well-understood. Once ambient temperatures exceed 26.7°C, however, compressor-based systems must work more, compromising efficiency, reliability and even shortening freezer lifespans. As compressors work harder, they produce even more heat. And as temperatures in these facilities rise, the HVAC systems will also have to work harder, leading to increased strain on the HVAC systems, higher energy costs and a vicious cycle of additional compressor work required to keep up. Once ambient temperatures exceed 32.2°C, system reliability can be compromised when using compressor-based units, placing vaccines at risk.

The HVAC factors are especially relevant to pharmaceutical distribution centers and healthcare systems, which are generally not equipped to handle ULT products (unlike biobanks). Since distribution centers are typically not equipped for such significant HVAC loads and the need for additional freezer space, this new challenge could involve unforeseen building modifications, which potentially can threaten the planned ULT deployment budgets and schedules managed by 3PL organizations.

An alternative choice is Stirling-cycle freezers. This technology (now over two centuries old, but substantially advanced by Stirling Ultracold), employs a frictionless moving piston that uses a linear displacement mechanism and a working fluid (helium), within a hermetically sealed container, to achieve ultra-low temperatures within the freezer closet. As there is no rotating compressor mechanism, the unit is relatively maintenance-free with no need for oil lubrication. The engine technology boasts precise performance across a wide temperature range (-86°C to -20°C, adjustable in 1°C increments) in higher operating ambient temperatures, and has been field-proven to ensure long-term sample safety in more than 15,000 freezer installations and over 250 million run-time hours.

Economics and efficiency

In terms of total cost of ownership, Stirling Ultracold ULT freezers are generally priced at a 20-30% premium over compressor-driven models. However, this initial premium is quickly offset with operating cost savings of 40% or more over the lifetime of standard compressor-based ULT freezers.  They have the capacity for more sample storage in the smallest footprint and connect directly to establish lab management programs for simpler monitoring. In 2017, Stirling Ultracold earned a 0.286 kWh/day/ft3 certification from Energy Star®, the lowest energy use and heat output per sample capacity of any certified ULT freezer and making the freezer a highly sustainable device.

Stirling Ultracold units come in a variety of models to best-fit the customer need. They are available as portable models (storage volume of 25 liter, 0.9 cu. ft.) for clinical use, compact, under-counter laboratory units (storage volume of 105 liter [3.7 cu. ft.) to larger upright biobanking units (storage volume of 780 liter [27.5 cu. ft.) The units can run on 120 or 240VAC to support global use, and remove the need for special personal protective equipment (PPE) required with CO2 or LN2.

One of the major reasons Stirling Ultracold has been selected as an early participant in this vaccine distribution is because of the uncertainty surrounding which vaccine candidates will be first available and what cold storage temperatures will ultimately be needed. Vaccine distributors are trying to “cover all their bases” and be ready the moment vaccine approvals arrive. Stirling Ultracold’s technology is being globally recognized as the only solution to offer a wide range of temperature setpoints, thus optimizing the storage temperature for the Covid-19 vaccine candidates currently within the approval pipeline.


About the author

Dusty Tenney is the CEO of Stirling Ultracold. He brings deep industry experience having held senior executive positions as SVP and president, respectively, within PerkinElmer and Brooks Automation. Prior work includes positions at GE Aerospace, AlliedSignal and Honeywell. Tenney holds a BS in Mechanical Engineering from the University of Maryland – College Park and a MS in Mechanical Engineering from the University of Vermont, where he worked for GE Aerospace and graduated from their Edison Engineering Program.