Vaccines are temperature-sensitive biological substances. Their successful delivery requires equipment that can maintain a stable temperature between 2°C to 8°C (35°F to 46°F). Known as the cold-chain equipment (CCE). This keeps vaccines cool and prevents freeze damage. CCE are categorized into active refrigeration systems and passive cooling devices.
Active systems involve the use of primary and off-grid refrigerators. Primary refrigerators are powered by the main electrical grid line power, while off-grid refrigerators are powered by kerosene, liquid petroleum gas, battery-powered solar, or solar direct-drive (SDD).
Passive cooling devices are either boxes or vaccine carriers. Cold boxes are larger around 6–25 L capacity, transported by motor vehicles, while smaller vaccine carriers of 0.5–3.5 L capacity are hand carried or carried by bicycles or motorbikes.
Unlike active system which require electricity or other sources of energy, passive devices require no other mechanism the cooling is through cold gel packs or frozen water packs
For decades now, immunization programs have been using passive containers with frozen packs for vaccine delivery. The World Health Organization (WHO) has prequalified 16 vaccine carriers, with sizes 0.80 L to 3.61 L for a smaller number of vaccines, and 21 cold boxes sized between 6.3 L and 24.4 L, used for larger quantities.
Both cold boxes and vaccine carriers need gel packs or ice packs to function. But using ice packs without proper conditioning increases the risk of freezing, which is dangerous for freeze-sensitive vaccines: diphtheria-tetanus-pertussis, tetanus toxoid, hepatitis B, pneumococcal conjugate, rotavirus, human papillomavirus, typhoid, cholera. Proper conditioning needs to thaw ice packs to 0°C.
A study conducted between 1990 and 2010 concluded that out of 35 temperature studies across the globe, 97% of those have an incidence of freezing in the cold chain.
Vaccines will be less potent if subjected to freezing temperatures. The WHO requires emerging technologies for vaccine transport to meet these criteria:
- Minimizes Freezing – Technologies that even with the use of frozen packs will not drop the temperature to freezing.
- With Larger Capacity – As more countries and as bigger population becomes involved with efficient immunization programs, the larger is the demand for vaccines around the world. Aside from less freezing, new technologies must also accommodate bigger volumes of vaccines.
- Point-of-use, small-volume vaccine storage – Having vaccines at the point-of-use in small health centers will enable far-flung areas to access vaccines. New devices must stay cold for days, weeks, or even months without electricity.
Manufacturers heeded the call for innovation of vaccine carriers and cold boxes. WHO, in partnerships with another global non-profit organization PATH, evaluated several of these new technologies in their demonstration projects in Vietnam, Tunisia, and Senegal.
Vietnam: Savsu Nano-Q™ Passive Cooler for Long-Term Storage
Nano-Q™ is a device that uses ice and state-of-the-art insulation materials to maintain temperature. United States-based Savsu Technologies designed and manufactured this product.
Project Optimize chose Nano-Q to be demonstrated in Vietnam because it can cool for seven days despite an ambient temperature of 32°C (89°F). Plus, the use of normal ice readily available from the nearest stores was helpful.
The project monitored the temperature of 12 Nano-Q devices in different commune health-centers in Vietnam. The researches then interviewed the users about their experiences.
The result was amazing. No freezing had been recorded for more than 65 months of cumulative monitoring. True to its promise, the device maintained the required temperature of the vaccines.
The users liked the fact that no electricity is required to run the device, therefore no fear of power outage spoiling the vaccines. The challenge according to users is the difficulty of purchasing ice during winter months in central and northern regions of Vietnam.
Tunisia: Domestic RCW 27 With Freeze Prevention for Vaccine Transport
In collaboration with the Ministry of Public Health in Tunisia, Optimize evaluated another new passive cooling technology. RCW 27 is a cold box manufactured by Dometic, a company based in Luxembourg. The RCW 27 is larger than RCW25 (WHO prequalified) and uses non-water phase-change material (PCM). PCMs are engineered to freeze at 5°C (41°F) to prevent vaccine freezing. The RCW 27 was made to maintain the temperature below 10°C (50°F) for more than 24 hours despite 43°C (109°F) surrounding temperature.
There were 5 RCW 27 in operation: two for Kasserine Regional Stores to the districts, and three from the districts to the health centers. The supplying stores were responsible for providing PCM packs to the device.
PCMs prove beneficial and challenging at the same. Unlike freezing packs, which needs to be conditioned according to WHO guidelines, the use of PCMs was much easier. Plus, there was no need for electrical connection all the time, as PCMs are efficient in its cooling.
The material was challenging in some way too. Since PCMs need to freeze at 5°C (41°F), they must be stored in a refrigerator and not in a freezer. To achieve this overnight, refrigerators need to be at 2°C (35°F), which according to health officials is too low for other vaccines stored in there. In that case, separate refrigerators were used to freeze PCM packs in each store. The users also noted that RCW 27 was heavy for hand-carry.
Senegal: Dometic RCW 25 Vaccine Carrier with PCM Packs For Vaccine Transport and Aircontainer Package System Bigbox-Container With PCM Packs
The government of Senegal started a project where the use of “moving warehouses” would improve their vaccine supply chain. The “warehouses” were equipped with two new passive cooling technologies: the 170 L Aircontainer Package System Bigbox-container and the Dometic RCW25 vaccine carrier.
Both containers are cooled by PCM packs. The larger Big-box container was used for short distances from the regional pharmaceutical store to health centers in Saint Louis, Richard Toll, and Dagana districts, due to having a shorter cold life of only 2.5 days.
The RCW 25 was used to deliver vaccines to remote places like Podor and Pété, both 325 km away from the regional pharmaceutical store.
In the chart below, temperature excursions were minimal. Both provided a stable temperature between 2°C (35°F) and 8°C (46°F).
While they liked the size of the two containers, the users suggested to the manufacturers to upgrade the hinges and locks of the Bigbox-container.
Apart from these new devices, several technologies are currently underway. Manufacturers will always have something to work on as long as users see the need for improvement. Manufacturers love the idea of having field-tests and live demonstrations.
As the need for passive cooling technologies with larger capacity and longer cold life arises yearly, more manufacturers are responding to the call for bigger and better storage and transport—all for the goal of delivering safe and potent vaccines.