Cold chain notes
- 1. Cold chain Definition It is a system of storage and transportation of the vaccines at recommended, low temperature (+2 to +8°C) all along from the time and place of the manufacture to the time and place of its use. There are three essential elements of cold chain like • Personnel: to organize and manage vaccine distribution • Equipment: to store and transportation of vaccine • Procedures: to ensure vaccines are stored and transported at recommended temperature. Cold chain includes: The cold-chain system consists of a series of transportation links with equipment and the persons concerned from the manufacturer to the point of use. Longer the chain, greater is the risk of cold-chain failure. The cold- chain equipment is so designed to keep cold air inside and to prevent warm air from entering. So when vaccines are placed inside this equipment, they are protected from heat and light. Figure 1: Links in the cold chain 1. Walk in freezers: Pre-fabricated modular polyurethane foam insulated panel assembled cold room with two identical refrigerator units and a standby generator set. Installation: National, State and Regional/Divisional Stores. Temperature maintained: -150 C to -250 C. Usage: Bulk storage of OPV Vaccine, Preparation of frozen Ice Packs for vaccine transportation. 2. Walk in coolers/ cold rooms: Pre-fabricated modular Polyurethane insulated panel assembled cold room, with constant electricity supply and two identical cooling units with standby generator. Maintain temperature of +2°C to +8°C.
- 2. Installation: Installed at government medical store depots, state & regional vaccine store. One such WIC has also been established for every 3 to 4 districts. Usage: Used for storage of large quantities of UIP vaccines. In India, under UIP usually WIC with capacity of 16.5, 32 and 40 Cubic meter are in use. Vaccines can be stored up to 3 months. 3. Deep freezer: Top opening lid covered container which operates on vapour compression system (220 volts A.C) Temperature maintained: -150 C to -250 C. Installation and use: Frozen ice packs kept permanently for increasing hold over time. Large deep freezers at district headquarters have been supplied for: Storage of OPV and preparation of ice packs. About 20 to 25 icepacks can be prepared by a 140 Liter DF in 24 hours with at least 8 hours of continuous electricity supply. Small deep freezers at PHC headquarters have been supplied for: Preparation of ice packs only 4. Ice lined refrigerator (ILRs): Ice lined refrigerators are lined with tubes or ice packs filled with water which freezes and keeps the internal temperature at a safe level despite electricity failure. These are top opening container with two sections (top and bottom), bottom of the ILR is the coldest part and in top portion, there is a basket. Installation: Used to store vaccines at district and sub-district level. Larger ILR is supplied to district headquarters and smaller ILR to PHC headquarters, based on the size and population. At the District level vaccines are stored for 3 months and at PHC level stored for 1 month. Temperature maintained: cabinet temperature between +2°C to + 8°C Usage: All the vaccines should be kept in the basket provided with the ILR. Vaccines like OPV, BCG, measles, and JE (in the sub-district stores, OPV is kept in ILR, unlike higher level vaccine stores, where it is kept in DF) can be kept at bottom of the basket while DPT, TT, Hep B, IPV and Pentavalent vaccines and diluents are kept in upper part of the basket.
- 3. 5. Domestic refrigerators: Installation: provided to every Primary Health Center, also used in urban dispensaries and by private practitioners in urban areas due to more assured power supply and non-availability of ILRs and DFs. Temperature maintained: +20 C to +80 C Usage: They can be used for storage of vaccine at private clinics and nursing homes, provided continuous power supply is ensured. 6. Cold box: Thick walled, thermally insulated boxes, lined with 24 ice-packs, which act as buffers and maintain the cold life inside the box for about 5 days. It does not have electrical connections. It has capacity of 5 - 22 liters that can store 1500 - 6600 doses. Installation: Cold boxes are supplied to all peripheral centers Usage: collect, store and transport large quantities of vaccines from one place to another place, by refrigerator- vans. Before the vaccines are placed in the cold boxes, fully frozen ice packs are placed at the bottom and sides. The vaccines are first kept in cartons or polythene bags. 7. Vaccine carrier: It is a square shaped box, made of insulating material. Four conditioned ice packs are placed inside the four side walls of vaccine carriers. At PHC level they are used for carrying vaccines (16-20 vials) and diluents from PHCs to session sites like subcenter or outreach sessions. Vaccines can be kept for a period of 12 hours, if not opened frequently. The ‘T-series’ of vaccines should be placed inside a polythene bag and closed with rubber band. The lid of the vaccine carrier is secured tightly. It should not be kept in the sun-light nor it should be opened frequently and unnecessarily. Day carriers Day carriers are used to carry small quantities of vaccines (6-8 vials) to a nearby session. Two fully frozen packs are to be used. It is used only for few hours period.
- 4. 8. Ice packs: These are flat plastic containers filled with water, up to the level marked on their sides. They are available in three capacities : 400ml, 500ml and 600ml. They have definite geometrical shape with two depressions in the center for finger grip. When the water is frozen into ice, it is then called ‘Ice-pack’. When placed in nonelectrical cold chain equipments such as vaccine carriers and cold boxes, help increase the holdover time. They are also used to keep reconstituted measles and BCG vaccine on the hole during an immunization session. Ice packs maintain cold-life for 5 days in cold box and for 1 day in vaccine carrier, if it is not opened. The risk of cold chain failure is greatest at sub-centre and village level. For this reason, vaccines are not stored at the sub-centre level and must be supplied on the day of use. Vaccine vial monitor (VVM): A VVM is a label containing a heat-sensitive material which is placed on a vaccine vial to register cumulative heat exposure over time. The combined effects of time and temperature cause the inner square of the VVM to darken gradually and irreversibly. Reverse cold chain: Maintaining the cold-chain in the reverse direction from the point of use to the vaccine testing laboratory. This is necessary, when the potency of the vaccine has to be tested. Reverse cold-chain also becomes necessary when stool specimen of a case of acute flaccid paralysis has to be sent to viral research laboratory for isolation of poliovirus, under AFP surveillance. OPV is considered as an ‘Indicator’ of quality of cold chain, as it is highly sensitive to heat and light.