Deep Dives

Cold Chain Equipment—One Size Doesn’t Fit All

Advances in cold chain equipment help deliver vaccines to the 1 in 5 children currently unvaccinated.

Keeping cool is a critical component of reaching children with potent vaccines. In areas where electricity is limited or unreliable, this can pose a significant challenge. As vaccines move through the in-country distribution system, power disruptions at any facility, or lack of cold storage during transport, can compromise vaccine potency and result in missed vaccination opportunities.

Research published in Vaccine shows there is no one-size-fits-all cold chain equipment that works for every facility in every location. Over the past 30 years, technology has evolved to take on these challenges in new ways, and the pace of innovation in cold chain equipment has picked up considerably over the past decade.

Solar battery-powered refrigerators were introduced years ago as a solution for vaccine storage in places without reliable electricity. But these models, while an improvement over other off-grid options such as gas- or kerosene-powered models, had their drawbacks. The average lifespan of the battery that stores solar power to operate the refrigerator is shorter than that of the refrigerator and solar panels, and required regular maintenance. This type of power is also subject to diversion, putting vaccine potency at risk.

To overcome these challenges, solar direct-drive refrigerators (SDDs) were developed to operate without batteries. Instead of capturing solar energy in batteries for later use, a SDD refrigerator uses solar energy immediately to freeze an ice lining around the refrigerator’s storage area. This “ice battery” can keep the refrigerator at proper temperatures for several weeks without additional solar power.

Passive cooling devices—cold boxes and vaccine carriers—have also long been a solution for keeping vaccines cool, particularly during transport. However, these have always been a temporary measure as the best-performing options have cold lives of 2–6 days for cold boxes and 17–50 hours for vaccine carriers. Recent advances in insulation materials have made possible a significant extension in the cold life of passive cooling boxes—up to 30 days without refreshing ice or cool packs. A cold life of 30 days both expands the possibilities for vaccine transport and provides an alternative for long-term stationary storage.

With the proliferation of cold chain equipment options, how can countries balance technical attributes and cost to decide where to invest their money? The World Health Organization and Gavi, the Vaccine Alliance both provide guidance for when countries should consider solar-powered options over electric mains-powered, ice-lined refrigerators (ILRs) based on the availability of electricity. For a country like Mozambique, where the most recent data show that businesses and institutions experience an average of 20 power outages every year, this is a major consideration.

Based on data from Mozambique using a sophisticated modeling tool called HERMES, researchers showed that despite a significantly higher purchase price, SDD technologies provide a lower cost-per-dose of vaccine administered anywhere one-day outages occur more than five times per year. They also provided cost savings at health facilities where two-day power outages occurred more than twice per year. As SDD technology continues to develop, if the cost of SDD decreases as the technology evolves, even fewer power outages would result in cost savings of the solar refrigerators over ILR.

All of these developments and findings point to one key consideration—as technological advances continue in cold chain equipment, communicating the capabilities and features of new equipment, relative to existing technology, is necessary. High-tech equipment may be glamorous, but today’s immunization supply chains need more than the latest developments. Customization is key.