Cold Chain & its Importance

Vaccines are the sensitive biological products which on exposure to deviation ( hot & cold) of recommended temperature causes active ingredients to degrade into inactive form. Vaccines are categorized into:

·       Heat sensitive vaccines: BCG, Oral polio vaccine, Rabies vaccine, etc.

·       Light sensitive vaccines: BCG, MR (Measles, Rabies) vaccines, etc.

·       Freeze sensitive Vaccines: Diluents, Hepatitis B, TT, DPT, etc.

                Vaccines are temperature controlled until use

Failure of vaccine

·       Deterioration of quality of vaccine during storage, transport & reconstitution of vaccine.

·       Multiple use / repeated use of vaccines

·       Cold chain failure

Based on composition of vaccines, the recommended temperature of each vaccine is different. Most of the common vaccines requires 2 to 8°C, Freeze dried vaccine needs -15 to-25 °C. Tissue culture vaccine require -196 °C.

 Introduction to Cold Chain

WHO states" It is a system of storing and transporting vaccines at recommended temperatures from the point of manufacturer to the point of use". It means that it is a temperature-controlled supply chain. It is very important component of an immunization program, since all vaccines lose potency over time, especially if exposed   to heat, and in addition also when they are frozen.

 It is the extension of Good Manufacturing Practice (GMP). Cold rooms, refrigerators, freezers, cold boxes and vaccine carriers must comply. 

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The cold chain system comprises three major elements:

•       Personnel: who use and maintain the equipment and provide service;

•       Equipment: for safe storage and transportation of vaccines; and

•       Procedures: to manage the program and control distribution and use of the vaccines.

Competent personnel and efficient procedures are a vitally important part of the cold chain system

  In order to maintain cold chain different tools and equipment have been developed.

1.     Ice packs: A water-pack frozen to a temperature between -5°C and -20°C before use. Icepacks are used frozen for the transport of oral polio vaccine (OPV) and used conditioned (see procedure for conditioning further down) for the transport of all other vaccines.

2.     Vaccine carrier: are insulated containers that, when lined with coolant packs, keep vaccines and diluents cold during transportation. These products are used for transporting vaccines from health facilities with refrigeration to outreach immunization sessions where refrigeration and ice are not available. Vaccine carriers are typically carried by a single health worker travelling on foot or by other means, where the combined journey time and immunization activity may range from a few hours to a whole day.

3.     Walk in Cooler: It is quite larger and helps in preparation of ice packs & bulk storage of vaccines. It maintain the temperature of -15 °C to -20 °C.

4.     Deep Freeze: maintains temperature of -15 °C to -20 °C helps to store ice packs and heat sensitive vaccines.

5.     Refrigerator/ ILR: Use alternate source of power supply for at least 8 hours in a day.  If it is not possible, then transfer the vaccines to cold box, which can hold the vaccines for 72 hours if not opened.  Most important component of cold chain. The temperature should be monitored twice daily. It maintains temperature at 2 to 8°C.

Method of Controlling cold chain

•       A cold chain can be managed by a quality management system.

•       Should be analyzed, measured, controlled, documented, and validated.

•       The food industry uses the process of Hazard Analysis and Critical Control Point, HACCP, as a useful tool.

•       Carriers and logistics providers can assist shippers. These providers have the technical ability to link with airlines for real time status, generate web-based export documentation and provide electronic tracking.

•       The use of refrigerator trucks, refrigerator cars, reefer ships, reefer containers, and refrigerated warehouses is common.

•       Shipment in insulated shipping containers or other specialized packaging.

•       Temperature data loggers and tags help

- monitor the temperature history of the truck, warehouse, etc. and the temperature           history of the product being shipped.

            - to determine the remaining shelf life.

•       Documentation is critical. Each step of the custody chain needs to follow established protocols and to maintain proper records.

Vaccine stability

All vaccines are sensitive biological substances that progressively lose their potency. This loss of potency is much faster when the vaccine is exposed to temperatures outside the recommended storage range. Once vaccine potency has been lost, returning the vaccine to correct storage condition cannot restore it. Any loss of potency is permanent and irreversible. Thus, Storage at the correct recommended temperature conditions is vitally important in order that full vaccine potency is retained up to the moment of administration. Although all vaccines are heat-sensitive, some are far more sensitive than others are. These vaccines become much more heat sensitive after they have been reconstituted with diluent. Some vaccines are also highly sensitive to being cold. Such vaccines will lose their potency entirely if frozen, although others can sustain freezing without any damage whatsoever. It is therefore vitally important to know the CORRECT storage conditions for each vaccine, and to ensure that each is kept always at the recommended conditions. Vaccines must not be frozen after reconstitution diluents for any vaccine must never be frozen. In addition to being temperature-sensitive, vaccines are also highly sensitive to strong light, and thus need to be kept in the dark as far as possible. Great care must be taken to protect them during use. As with loss of potency due to heat, any loss of potency due to light is also permanent and irreversible. Note that all losses of potency are CUMULATIVE .Each time exposed to incorrect temperature or strong light; potency decreases. Since the vaccine may have already been exposed previously, any new exposure, however small, will increase the damage to the vaccine. Ultimately, due to cumulative damage, the vaccine may be completely destroyed, with all its potency lost. Note also that even when stored at the correct temperature vaccines do not retain potency forever.Therefore the expiry date marked on a vial or packet of vaccine must be strictly observed even when correct storage temperatures have always been maintained.

Things to Remember

·       Never use other diluent.

·       Diluent must be cold, between 0 and 8 degrees Celsius, before being mixed with the vaccine.

·       When reconstituted, the vaccine must be used within 6 hours, and any remainder discarded

·       All vaccines lose potency gradually, even at correct Storage temperatures - observe expiry dates.

·       All vaccines suffer much faster loss of potency when exposed to temperatures above +8 degrees C.

·       Any loss of vaccine potency is irreversible.

·       Damage due to successive exposures to heat or light is cumulative.

Even the most expensive and sophisticated equipment will not ensure an effective cold chain if  not correctly used and managed by health person

Significance of Cold Chain

Ø  Storing and transporting vaccines

Ø  Protection from sunlight exposure

Ø  To assure potency

Ø   To ensure maximum effectiveness after immunization

Ø  Safety and Vaccine stability