TechNet-21 - Forum

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  1. Optimize.WHO
  2. Cold chain equipment
  3. Monday, 11 April 2011

by Steve McCarney, John Lloyd, and Joanie Robertson, PATH

A group of public- and private-sector partners are collaborating with project Optimize to evaluate a range of innovative transportation and storage containers for heat-sensitive drugs and vaccines that operate in environments with or without access to reliable power. The following is a brief description of each technology, the niche it was designed to fill, and the context in which it will be tested.

Stationary passive coolers

Commune-level passive cooling in Vietnam

Currently in Vietnam, not all commune health centers have the capacity to provide vaccine cold storage for a full month. Vaccines are generally brought in for one- or two-day immunization sessions as part of the monthly national immunization strategy. However, it is important for certain vaccines (such as hepatitis B) to be available throughout the month so that babies can receive necessary vaccinations at birth.

With support from Optimize, the National Expanded Programme on Immunization is evaluating the appropriateness of new small-volume (about 3 to 4 liters) passive cooling devices, creating capacity to store a small number of vaccines all month at the communes. These devices provide approximately one to four weeks of cooling on one “charge” of ice. In this way cooling can be provided with no requirement for a refrigerator or even an on-site energy supply.

It is anticipated that these coolers will improve on-time delivery of hepatitis B birth dose while also decreasing closed-vial wastage. The intervention would not increase cooling energy use at the commune, would be compatible with intermittent power conditions, and would not disrupt the current monthly immunization-day system which is working very well.

Mobile passive coolers

Passive cooling for vaccine transport in Tunisia

To safely transport new vaccines, Tunisia’s EPI program is working with Optimize to evaluate phase change material (PCM) packs as a possible passive cooling storage alternative to ice packs. Similar to ice, solidly frozen PCMs hold more cooling power than when in the melted or liquid phase. PCMs are ideal because they can freeze at a vaccine-safe temperature (e.g., +5°C) and can have direct contact with freeze-sensitive vaccines, allowing the entire box area to be used for vaccine. Traditional cold boxes can substitute PCM packs for ice packs and provide adequate cooling for up to 15 hours in the heat of the Sahara.

Insulated containers on Senegal’s moving warehouses

The Ministry of Health in Senegal is piloting a “moving warehouse” approach. Rather than requiring health post staff to pick up vaccines, antiretrovirals, malaria, and tuberculosis medications, along with associated supplies from a district center, two trucks serve as moving warehouses and distribute supplies from the regional level to health posts in all five districts of the Saint-Louis Medical Region.

Integral to the moving warehouse concept is the use of large rolling insulated containers to transport necessary drugs and vaccines. These containers can be rolled by workers or handled by forklift. With a capacity of 161 liters, the volume of one rolling container is equivalent to eight long-range traditional cold boxes, which saves space in transit and makes it easier to handle larger volumes of bulkier single-dose vaccines. The containers are cooled by PCMs that have been chilled in a refrigerator at safe temperatures for a specified time. The PCM panels are placed in the container, and vaccine can be loaded in direct contact with all inside surfaces of the rolling container. Currently, trucks equipped with these containers are able to keep vaccines at proper temperatures for as long as six days while on the road. And in areas where roads are poor, moving warehouses equipped with passive containers have a lower maintenance burden and higher reliability compared to insulated trucks with active refrigeration.

Active refrigeration

Ice-lined refrigerators in Senegal

Power problems that occur throughout the developing world, including in Senegal, make it challenging to cool vaccines and heat-sensitive drugs with electric refrigerators. In this type of intermittent power setting, conventional practices often rely on diesel generators to back up unreliable grid electricity. However, generators are costly, difficult to maintain, create noise and air pollution, and subject to fuel supply disruptions and diversions.

In Senegal’s St. Louis region, a more reliable and energy-efficient solution for vaccine storage is being demonstrated: the super long-life ice-lined refrigerator (ILR). ILRs provide stability in intermittent power conditions and their cost is minimal in contrast with absorption-type refrigerators powered by electricity, bottled gas, or kerosene. The use of ILRs with longer-than-average holdover times can eliminate the need for backup generators if grid electricity provides at least eight hours of power on average per day. The best-in-class ILR can operate with just four hours of electricity and provide over ten days of holdover to maintain acceptable vaccine temperatures, even in warmer climates. Particularly in settings where electricity is unreliable, the ILR is a safer, more reliable choice for vaccine storage than domestic refrigerators.

Domestic fridge study in Tunisia

Many countries, including the United States, are using untested, unmonitored domestic-style refrigerators for storing vaccine and reporting significant losses due to poor temperature control. The WHO Performance, Quality and Safety (PQS) program has established equipment standards and testing protocols for vaccine refrigerators including electric, ILRs, gas/kerosene, and solar-powered refrigerators. Using these PQS prequalified refrigerators is the recommended approach for purchasing vaccine storage refrigerators.

However, many countries elect to purchase locally available refrigerators because these are usually less expensive, quickly available, employ front opening doors, and are familiar to local service technicians. Unfortunately, few of these domestic-type refrigerators are sufficiently monitored to ensure safe vaccine temperatures.

Monitoring has shown that domestic refrigerators have widely varying temperature performance and can expose the vaccine to freezing temperatures and rapid warm-up after power cuts. The widespread practice of domestic refrigerator use warrants better temperature monitoring to find and isolate problem refrigerators before they damage vaccines.

In Tunisia, Optimize is working with Centre Technique des Industries Mécaniques et Electriques (CETIME), a government-sponsored laboratory, to use WHO PQS protocols to test typical domestic refrigerators that have been used for vaccine storage or are being considered for future purchases.

Domestic refrigerators already in use are also being monitored, and their performance will be evaluated. Evaluation results will help Tunisian decision-makers assess the risk of using domestic refrigerators, and laboratory testing of new models will identify potential risks as well as help to inform solutions for maintaining acceptable temperature control. If no suitable refrigerator or solutions can be identified, decision-makers have evidence to make the case to develop improved models in country or to purchase WHO PQS prequalified refrigerators. The demonstration in Tunisia is intended to convey to all countries using domestic refrigerators that first, they should all be continuously monitored in use; second, they should be tested and their performance confirmed before procurement; and third, they should meet the global WHO/PQS norms for vaccine storage.

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