Cold Chain

Vaccines are made from micro-organisms similar to the ones that cause disease, or from the toxins that bacteria produce. Therefore, all vaccines are sensitive biological substances that progressively lose their potency (i.e. their ability to give protection against disease). This loss of potency is much faster when the vaccine is exposed to temperatures outside the recommended storage range.

In addition to being temperature-sensitive, several vaccines are also highly sensitive to strong light, and thus need to be kept in the dark as much as possible. They are given some protection by being supplied in vials of dark brown glass to reduce the penetration of light, but this alone will not prevent light damage however and great care must be taken to protect them during use.

Each exposure to extreme temperature or strong light results in some degradation of the vaccine. Furthermore, each exposure to inadequate conditions has a cumulative impact on vaccine potency. Once vaccine potency has been lost, returning the vaccine to correct storage condition cannot restore it. Vaccines do not change their appearance when losing its potency so it is not possible to see whether a vaccine in a vial has lost its potency without a complete laboratory test. Any loss of potency is permanent and irreversible.

The temperature range required for each vaccine is established by the manufacturer. Most of the vaccines require between +2°C and +8°C, but this may vary according the vaccine and the storage times. For example, some vaccines can be stored at-15°C to -25°C in a central storage, up to 6 months, but only up to 1 month at 0°C to +8°C, in a District and Health Centre storage. Oral Polio vaccine may be thawed and frozen again without danger to the vaccine. Some other vaccines like Inactivated Polio, Diphtheria-pertussis-tetanus, Diphtheria-tetanus, Hepatitis B and Tetanus vaccines are seriously damaged by being frozen at temperatures below 0°C. Always refer to the vaccine manufacturer specifications to store the vaccine within the suited temperature ranges during the appropriate timeframes.

The cold chain includes all the equipment and practices used to ensure a constant temperature for a product that is not thermostable (such as vaccines, serums, tests, etc.), from the time it is manufactured until the time it is used. It also includes all the temperature monitoring equipment and routines.

Health workers and logisticians involved in vaccines management are responsible for maintaining the adequate storage and transport conditions: while vaccines are stored in the vaccine stores at the province and county levels, or while they are being transported to township and villages, and while they are being used during immunisation sessions or rounds.

All relevant staff must be trained to both use and manage the cold chain equipment and to regularly monitor the temperature. This includes having appropriate and efficient logistics mechanisms to manage shipping, fuel, spare parts etc.

Common Terms in Cold Chain

Cold Box

Insulated containers that can be lined with coolant packs to keep vaccines and diluents cold during transportation and/or short period storage. Cold boxes are used to collect and transport vaccine supplies from one fixed vaccine store to another, and from vaccine stores to health facilities. They are sometimes also used to temporarily store vaccines when the refrigerator is out of order or being defrosted.

Cold Chain

Equipment and practices used to ensure a constant temperature for a product that is not thermostable (such as vaccines, serums, tests, etc.), from the time it is manufactured until the time it is used. It also includes all the temperature monitoring equipment and routines.

Cold Life

The number of hours the temperature inside a passive cold chain container stays below +8º C. This depends on the ambient temperature, the number of times the box is opened and for how long, the number and temperature of the ice packs used, but also on the quality of the box, how well it closes and insulates. Cold life tests are performed at +43º C. Do not confuse “Cold life” with “Cool life”.

Cool Life

The number of hours the temperature inside a passive cold chain container stays below +20º C.

Coolant Pack

Also referred as “ice packs”, are flat, square plastic bottles that are filled with water and cooled. They are used to keep vaccines cool inside the vaccine carrier or cold box.

Decommission

The process of planned removal of equipment from an active status and its storage in a secure and safe place until disposal.

Disposable Insulated Carton Box

Passive cold chain portable container used by producers to ship their vaccines around the world. Generally, they consist of a polystyrene box inserted in a cardboard box for transport of large quantities of vaccines in favourable circumstances (e.g. in an airplane). They have a limited cold life (often with a maximum of 4 days).

Lot Release

The process of national regulatory authority evaluation of an individual lot of a licensed vaccine before giving approval for its release on to the market.

Summary Protocol

A document summarizing all manufacturing steps and test results for a lot of vaccine, which is certified and signed by the responsible person of the manufacturing company. Also called “lot summary protocol”

Vaccine Carrier

Small cold boxes, portable by one single person, used to keep the vaccine cold for short transport, or to store vaccines temporary just before vaccine administration. There are many types.

Expanded Programme on Immunization (EPI)

Global program initiated by WHO with the objectives to ensure immunization of all children against certain diseases (such as measles, rubella and tetanus) and to eradicate poliomyelitis, and to extend all new vaccine and preventative health interventions to children in all districts in the world.

WHO PQS

WHO audited and pre-qualified medical equipment based on Performance, Quality and Safety (PQS) requirements. The list of validated equipment is accessible online and used by several agencies as reference for procurement.

Ready-to-use Vaccine

Vaccines that come as a liquid and are ready to use in the person.

Reconstituted Vaccines

The vaccines that come in a lyophilized (or freeze-dried) state and need to be reconstituted at the vaccination site. The latter come in two vials: one for the lyophilized vaccine, the other containing the diluent (saline solution).

Solar Direct-Drive (SDD)

Refrigeration technology for solar powered devices that avoids the batteries for energy storage.

Vaccine Preparation

The process of mixing freeze-dried vaccine with the diluent. Consider that vaccine produced by one manufacturer must never be used with diluent produced by another.

Sensing/Monitoring Equipment

Specialized instruments that remotely monitor and log data on cold chain facilities, including ongoing inside/outside temperatures, and temperature events.

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