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Cold Chain and Refrigeration

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This solar powered vaccine refrigerator installed by the World Health Organization at Port Salut in Haiti has worked well for two years. (Photo: This email address is being protected from spambots. You need JavaScript enabled to view it.

Health facilities in developing countries need to maintain the cold chain to ensure that critical medicines, vaccines and supplies can reach those in need.

Vaccines are sensitive to both heat and cold and so need to be kept between 2°C and 8°C from the point of manufacture to the point of use. The recent global push to deliver anti retroviral drugs and services to HIV-positive patients worldwide has introduced new cold chain requirements. Blood, HIV rapid test kits, pediatric ARV drugs, and a variety of testing reagents all must be stored in climate controlled conditions. Properly refrigerated and stored blood is critical to HIV treatment efforts in developing countries. In order to keep blood useable, blood bank refrigerators need to keep internal temperatures between 2°C to 6°C all day, every day.

The system for keeping these critical supplies at the proper temperature is called the cold chain. For years, health professionals have struggled to develop the cold chain in developing countries to ensure that critical medicines and vaccines could reach those in need. Lack of access to electricity and intermittent power supply greatly complicate establishing a cold chain in many developing countries with traditional electric refrigeration.

 

Medical Products that are Cold Chain Dependent 

A variety of medical products require constant temperature control throughout their distribution chain. These requirements are typically very narrow (a few degrees Celsius), and the successful delivery of such products depends on careful planning, proper procedure and appropriate technology. This section outlines some common medical products that rely on the cold chain for their dispersion and comments on their particular temperature requirements. The products listed here are essential tools of modern health care, and are often used in combination in order to achieve effective results. Through these products, the cold chain becomes an integral part of improving human health worldwide.

Product Description
Vaccines All vaccines degrade over time, depending on the temperatures to which they are exposed. Although some vaccines are more sensitive to temperature than others, if kept within 2°C and 8°C most will remain stable for a year or more. While high temperatures adversely effect the useful life of vaccines, freezing temperatures will also damage many common vaccines, including those for: Hepatitis B, Diphtheria, Influenza and HPV. Using appropriately designed refrigerators and temperature monitoring equipment will help to ensure that vaccines are kept within narrow temperature constraints.
Whole Blood Whole blood is another common cold chain dependent substance that is vital to community health. Blood must be kept within 2°C to 6°C in order to be safe and effective for transfusion. If exposed to temperatures greater than 6°C, blood's ability to carry oxygen is greatly reduced and the probability of bacterial contamination is heightened. Furthermore, exposure to freezing temperatures will render blood useless and the transfusion of such blood could be fatal. For these reasons, the proper storage and transport of blood within the cold chain is essential. Standards for refrigerators, cold boxes and temperature monitoring equipment for use in the blood cold chain are key to ensuring that blood used in transfusions is safe and reliable.
Blood Derivatives Other blood products, such as platelets, cryoprecipitate, plasma and plasma derivatives all have stringent transport and storage temperature requirements. Plasma and plasma derivatives typically require a temperature range the same as that of whole blood. Cryoprecipitate (another type of plasma derivative) needs to be kept at a temperature no greater than -20°C while platelets must be kept within 20° and 24°C. Equipment specifically designed to meet the needs of these products should be used throughout their supply chain.
HIV Test Kits and ARV Drugs HIV test kits and pediatric ARV drugs are integral tools in the effort to reduce HIV infection rates around the world. These cold chain dependent supplies vary in their sensitivity to temperature, but most HIV test kits require storage at 2°C and 8°C. As with vaccines, this narrow temperature range will be best maintained through the use of appropriate cold chain equipment.
Testing Reagents Reagents, used in laboratory testing also have cold chain requirements. Temperature specifications vary depending on the type of reagent and the manufacturer. Manufacturer's guidelines on the transportation and storage of reagents should be followed and appropriate equipment selected based on those guidelines.

 

Standards Relevant to Cold Chain Equipment 

In order to help designers and implementers of cold chain equipment, the World Health Organization (WHO) has developed a number of standards for equipment used to store, transport and monitor cold chain dependent products. These standards provide a basis for the procurement of quality equipment designed to meet the stringent specifications necessary for a robust and effective cold chain.

The following table lists each of the relevant WHO standards by category. Each listing is also a link to the standard itself. Additionally, a link to a listing of WHO pre-qualified equipment is provided for each category.

Note: Standards E01, E03 and E04 are applicable only to vaccine cold chain equipment, as blood has different cold chain requirements.

Category Equipment Covered

E01 Cold rooms, freezer rooms and related equipment

E03 Refrigerators and freezers for storing vaccines and freezing icepacksPrequalified equipment

  • WHO/PQS/E03/FZ01.2: Vaccine freezer or combined vaccine/icepack freezer: compression cycle

  • WHO/PQS/E03/FZ02.2: Icepack freezer

  • WHO/PQS/E03/RF01.2: Refrigerator or combined refrigerator-icepack freezer: compression cycle

  • WHO/PQS/E03/RF02.2: Refrigerator or combined refrigerator-icepack freezer: absorption cycle

  • WHO/PQS/E03/RF03.2: Ice-lined refrigerator or combined refrigerator-icepack freezer: compression cycle

  • WHO/PQS/E03/RF04.2: Refrigerator or combined refrigerator-icepack freezer: compression cycle. For solar powered rechargeable battery storage

  • WHO/PQS/E03/RF05.2: Refrigerator or combined refrigerator-icepack freezer: compression-cycle. For solar direct drive without battery storage

  • WHO/PQS/E03/RF06.1: Refrigerator or combined refrigerator and water-pack freezer: compression cycle. Solar direct drive with ancillary rechargeable battery

  • WHO/PQS/E03/PV01.2: Solar power system for compression-cycle vaccine refrigerator or combined refrigerator-icepack freezer

E04 Cold boxes and vaccine carriersPrequalified equipment

E05 Ice-packs, cool-packs and warm-packsPrequalified equipment

E06 Temperature monitoring devicesPrequalified equipment

 

Considerations when Choosing a Blood Bank Refrigerator 

When choosing a cold chain refrigerator for blood or vaccine, there are many factors to consider. A refrigerator must be properly sized to both meet the refrigeration needs of the facility and fit within the facility's overall energy system capacity. Another key considerations is holdover time, which must be appropriate for the reliability of the facility's energy supply; if the facility receives intermittent power, a longer holdover time will be required. Further issues include: temperature zone (based on the regional climate), daily icepack freezing capacity, reliability and price. A thorough analysis of all of these considerations will help to ensure the sustainability of the facility's cold chain refrigerator.

Consideration Description

Size and Energy Use

Refrigeration requires significant energy and choosing a refrigerator which is properly sized for the intended need is critical. Oversized blood bank refrigerators have been observed in many developing countries.  Use the vaccine storage capacity or blood storage capacity of the refrigerator, typically reported in liters or number of packs, to choose a unit properly sized for the needs to the facility.Manufacturers should state the typical energy consumption, in kWh, per 24 hours.  These data should be available for both stable running conditions (i.e. maintaining constant temperature) and contents cool down (i.e. freezing or cooling the refrigerator contents), and should reflect performance at the maximum rated ambient temperature for the equipment (temperature zone rating).  Energy consumption will vary based on refrigerator capacity and type; sufficient manufacturer's data should allow for a fair product comparison based on energy consumption.For examples of typical cold chain refrigeration loads, as well as other loads associated with blood banks, see Blood Bank Load Calculations and Blood Banks and Blood Safety.  Also see WHO prequalified equipment: refrigerators and freezers for examples of specific product data.  Use our Load Calculation and System Optimization tool to better understand the effect refrigeration loads will have on your facility.

Intended Use

The cold chain requirements for blood and vaccine differ slightly; blood must be kept at 2°C to 6°C while vaccine must be kept at 2°C to 8°C.  While this difference may seem minor, it can make a large difference in the delivery of usable blood.  If a refrigerator is intended to be used for the storage of blood, a unit designed for that purpose should be chosen, as proper storage conditions cannon be guaranteed otherwise.

Temperature Zones

Understand temperatures zones when evaluating equipment. Equipment is rated to maintain required storage temperatures under ambient temperatures for various climate types. For example, hot zone rated equipment must be perform when subjected to ambient temperatures of up to 43°C; temperate and moderate zone temperature thresholds have also been developed. Temperatures/geographic zone determinations should be based on the prevailing climate of the area. The figure to the left shows the WHO temperature zone labeling requirements. Hot zone equipment can be used in temperate zones, but equipment for temperate zones should not be used in hot zones unless care is taken.

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World Health Organization temperature zone labels. (Source: WHO PQS performance specification standards).

Vaccine Storage Capacity

Vaccine storage capacity is often reported in liters.  This is a primary consideration when choosing a medical refrigerator.  Storage capacity should align with the needs of a particular facility.  Undersized units will compromise the viability of the cold chain, while oversized units may stress the facility's energy system.

Daily Icepack Freezing Capacity

Capacity is crucial if large quantities of frozen icepacks are needed and/or when the appliance is also used for vaccines.  If the program requires only icepack freezing, and capacity is not a major concern, any locally available freezer with low power consumption can be used.According to WHO standards, any combination refrigerator and icepack freezer should be able to freezer at least 1.6 kg of icepacks per day.  Dedicated vaccine/icepack freezers should have a daily freezing capacity of 7.2 kg, while icepack-only freezers should freeze 2.4 kg/day.

Power Source/Quality

Equipment should be selected that is compatible with the available power supply.  Refrigerators typically run on 110-120V or 220-240V AC power at 50 or 60 Hz, and these operating specifications should match the power supplied to the facility.  If the facility is connected to the grid or a generator, voltage stability may be an issue.  If the power supply frequently generates surges, dips or other fluctuations in voltage, the refrigerator may be damaged.  In this case, an automatic voltage regulator (AVR) should be connected to the refrigerator in order to ensure that it receives high quality power; some manufacturers offer AVRs as an option.Refrigerating equipment designed specifically for use with a dedicated solar system run on 12V or 24V DC power.

Holdover Time During Power Failures

Continuous refrigeration is required for vaccine storage, and it is often difficult to ensure this in areas where power sources are intermittent or fuel is of poor quality. Ice-lined refrigerators can provide stable refrigeration even in areas of intermittent power. The longer the "holdover time" of the refrigerator, the better the chances the vaccine will survive a power outage.According to WHO standards, a standard compression medical refrigerators should have a holdover time of no less than 4 hours.  Ice lined refrigerators should have a holdover time of at least 20 hours.  Solar powered refrigerators should have a holdover time of 3 hours if connected to a battery, and 20 hours if directly supplied by PV panels (i.e. no battery).

Reliability/Spare Parts

Know the availability of spare parts and the proximity of repair facilities.  Spare parts and repairs account for 40 - 50% of the whole-life cost of a refrigerator.  To avoid shortages later, purchase these spares at the time the equipment is purchased.  Manufacturers should suggest necessary spare parts.  Typical spare parts include thermostats, compressors and fans.

Price

Include freight costs and freight times in cost evaluations. When placing your order, include a request for a thermometer; order a voltage stabilizer for electrical equipment if local conditions require one.

Training

Are the users and those in charge of maintenance of the equipment properly trained? The importance of user and technician training is often underestimated and therefore under-budgeted.  A cold chain system with good equipment but insufficiently trained staff may seriously hamper an immunization program.  Remember to specify the language of the user's and service manuals.  For more information, see the World Health Organization's: Manual on the management, maintenance and use of blood cold chain equipment

CFCs

All models that meet the Montreal Protocol standards are CFC-free. Acceptable refrigerants are R134-A and R410-A.

 

Types of Cold Chain Refrigerators 

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Blood bank refrigerators come in many different sizes. The size of the refrigerator is typically closely correlated to its energy use. (Photo: This email address is being protected from spambots. You need JavaScript enabled to view it.

A variety of different refrigeration technologies have been developed in order to extend the cold chain to areas with limited energy services including, 12 V electric, LPG, gas electric hybrid, and kerosene powered models. A cold box can also help keep vaccines at the required temperature for between two and seven days and is needed in case of interrupted power supply, equipment maintenance. They can also be used to supply health posts without refrigeration, provided the vaccine is to be used immediately.

Each of these refrigeration technologies has advantages and disadvantages and there is a healthy debate among health professionals concerning the most reliable technology.

Evaluation of in several countries has highlighted the following observations:

Type Description

Standard Compression

Compression refrigerators and freezers require a source of electricity to run a compressor, and can be powered either by AC or DC power. AC refrigerators can be operated by grid power or by battery power through an inverter. DC refrigerators can be powered directly by batteries. Compression refrigerators for medical use are heavily insulated, and include cooling fans and temperature monitoring equipment. Some medical refrigerators have two compressors to provide redundancy in case one compressor fails. Compression refrigerators are the best option when there is a high quality electricity supply, either from the grid or an on-site energy supply system specifically designed to meet refrigeration loads.

  • Minimum holdover time: 4 hours

Solar Compression

Solar electric refrigerators are a type of compression refrigerator. They are self-powered units that typically include a top-opening refrigerator with no internal fans or lights; solar panels, and/or batteries. Solar refrigerators require careful study of the refrigeration requirement, number of sunlight hours, and a specification of the number of days of storage for cloudy periods. Solar refrigerators also require the use of high-quality batteries and battery charge control equipment, properly sized electrical wires, and a supply of spare parts. The figure below outlines some important considerations when determining if a solar refrigerator is an appropriate cold chain solution.

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Solar refrigerator decision flow chart. (Source: Adapted from WHO-EPI Product Information Sheets, 2000)

WHO standards for solar powered refrigerators distinguish between systems with batteries and systems without batteries:

Battery storage solar systems require proper PV panel and battery bank sizing to provide power for periods without sufficient sunlight. Such systems rely on energy stored in the batteries, rather than the holdover time of the refrigerator, to ensure that temperatures are maintained.

  • Minimum holdover time: 3 hours

Direct drive solar systems, those that do not rely on battery storage, require greater holdover time and are also specified based autonomy. Autonomy is the number of days that the refrigerator can maintain required interior temperatures when solar radiation is low. For instance, if a refrigerator requires a minimum of 3.5 kWh/m2/day of solar irradiance in order to perform properly, the autonomy is the number of days that interior temperatures will be maintained if solar irradiance is below that minimum condition.

  • Minimum holdover time: 20 hours

  • Minimum autonomy: 3 days

Solar refrigerators are an excellent option for remote facilities without access to reliable electricity or fuel supplies if all the conditions for maintaining and sustaining the solar systems are also in place. WHO/UNICEF supported solar powered vaccine refrigerators are typically the most successful example of solar power application in rural health facilities. While solar/PV powered refrigerators still suffer from all the challenges detailed on this site - they can be very effective when installed as part of a nationwide cold chain program with associated support mechanisms. These systems are typically more sustainable than standard clinic-wide solar/PV systems for the following reasons:

  • Dedicated Load - The systems are typically well designed (oversized) for the vaccine refrigerator and no other load is allowed to be connected. This prevents system overloading which results in the failure of many clinic wide systems. 

  • Maintenance Staff - WHO/UNICEF cold chain programs typically train local technicians who are responsible for the cold chain. These technicians make periodic checks of each cold chain system, including the solar system. Technicians are often supported by a national level cold chain technician who can provide support when difficult problems are encountered.

Ice Lined Compression

Ice lined refrigerators are designed to have a longer holdover time. Unlike standard electric medical refrigerators, they may hold the temperature below +10°C for many days following a power cut. This is achieved by lining the cabinet with water/ice containers or freezer sections with ice packs positioned adjacent to the storage area. During periods of power failure and load shedding, the ice packs act as a means of cold storage to protect the units stored in the refrigerator. Ice lined refrigerators are strongly recommended for facilities located in areas with intermittent power supply (i.e. eight or more hours of reliable electricity per day) and frequent power cuts, typically in district or regional centers.

  • Minimum holdover time: 20 hours

Absorption

Absorption refrigerators require a heat source, which is typically either a natural gas, kerosene or propane burner, but which can also be supplied by an electric resistive heater. Kerosene refrigerators are more difficult to control than propane refrigerators, and electric absorption refrigerators are typically less efficient. Absorption refrigerators are an excellent option for areas with no power or for which solar refrigeration is not feasible, but which have access to fuel, although funds to purchase the fuel can be a serious constraint.

  • Minimum holdover time: 1.5 hours

Hybrid

Hybrid absorption/compression refrigerators can operate on either electricity or gas. These refrigerators offer the flexibility of operating on whichever energy source is available at the lowest cost. They are a good option for any type of small facility with inconsistent electrical power. Supply of fuel is still an issue, however, as hospital staff often consider it a "back-up" and do not prioritize refilling canisters. WHO standards for absorption refrigerators apply to hybrid refrigerators.

Standard Domestic Compression

Domestic refrigerators are not as reliable or efficient as medical refrigerators, but are often more easily available and less costly. They may be of the compression or absorption type, and are typically front-opening with poorly insulated magnetic seals. Because domestic refrigerators are usually poorly insulated, internal temperatures can rise quickly during failures and result in uneven temperature distribution, including cold spots in some parts of the unit. Domestic refrigerators are a suitable option when high-quality AC power is available and reliability is not critical and thus should not be used for blood storage.

Ice Pack Freezers

Ice pack freezers are available as either compression or absorption type units. These freezers are suitable only for the freezing and storage of ice packs, although some compressor-type models are also designed for freezing vaccine. Because ice pack storage is not as critical as vaccine or blood storage, these units are typically less complex and have less stringent requirements than medical-grade refrigerators. There are WHO standards in place for ice pack freezers but no minimum holdover time is specified.

Cold Boxes and Vaccine Carriers

Cold boxes and vaccine carriers are not refrigerators, but are highly insulated containers used to transport vaccines from one facility to another, or from a facility to the point of use. These containers are rated by their cold life, or the number of hours they can maintain required internal temperatures (much like holdover time). Cold life ratings can be further divided by long range and short range, which indicate the relative distance over which they can be relied on for transport. WHO has set forth the following minimum cold life requirements:

  • Cold box, long range: 96 hours

  • Cold box, short range: 48 hours

  • Vaccine carrier, long range: 30 hours

  • Vaccine carrier, short range: 15 hours

 

Temperature Monitoring Equipment 

Temperature monitoring is a crucial part of ensuring an effective cold chain.  There are a variety of methods and technologies that have been developed to monitor temperature during the transport and storage of cold chain dependent products.  Twice daily manual temperature readings and continuous automatic data logs are two examples of such methods, either can be accurate and effective but both require defined procedures and appropriate equipment.  Described below are just a few of the temperature monitoring technologies available, for more information on these and other devices the section on WHO cold chain standards above, or WHO prequalified equipment: temperature monitoring devices.

Note that many cold chain refrigerators have integrated temperature measurement systems, these systems should be closely evaluated when choosing a refrigerator.

Device Description
Portable Electronic Thermometer Portable thermometers are a simple and inexpensive solution to cold chain temperature monitoring. When used as a part of a well organized temperature monitoring protocol, involving twice-daily temperature recordings, these devices can be used to effectively track temperature across multiple cold chain storage units. While the devices themselves are quite accurate, the necessary opening and closing of cooling compartments when taking measurements can lead to inaccurate results. Other drawbacks are that a portable device can be lost or stolen and does not allow for continuous temperature recording, leaving the monitoring program open to human error.
Fixed Pressure Dial Thermometer A fixed pressure dial thermometer is an analog device that displays the temperature within a single refrigerator at all times. This dedicated device allows for the manual recording of refrigerator recording, without the drawback of having to open the cabinet door.
Integrated Electronic Thermometer An integrated electronic thermometer is similar to the fixed dial thermometer above, but has a digital temperature display. Some dedicated electronic thermometers also record the minimum and maximum temperature within the storage cabinet over a period of time, giving greater assurance that storage temperatures have not gone outside of the required temperature range.
Thermograph A thermograph is an analog device that continuously records temperature over a period of time, typically 24 hours or 7 days. These devices allow for a complete record of storage temperature for a single, or in some cases, multiple refrigeration units. One major drawback is the need for special recording paper, pens and ink, which can run out over time, rendering the device useless.
Temperature Data Logger A temperature data logger allows for continuous temperature monitoring. Much like a thermograph, a data logger can track the temperature for one or more refrigeration units, maintaining a constant temperature record for each. The advantage of a data logger is that it does not require consumables like ink and paper, as does a thermograph. Access to a computer and appropriate data logging software are essential, however.
Alarm An alarm is an audible or visual indicator that alerts facility personnel if the temperature within a storage unit is outside the required temperature range. Alarms can also be used to indicate when a refrigerator door has been left ajar, or when a unit experiences a loss of power.

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