Cold chain
Introduction
The "cold chain" is a system of storage and transport of vaccines at low temperature from the manufacturer to the actual vaccination site. •The cold chain system is necessary because vaccine failure may occur due to failure to store and transport under strict temperature controls. •Among the vaccines, polio is the most sensitive to heat, requiring storage at minus 20 degree C.
Deep freezer (300 Iltr ) and Iced lined refrigerators ( ILFs 300/240 Itr capacity)
These helps to supplied to all districts and the WIC locations to store vaccines. Deep freezers are used for making ice packs and to store OPV and measles vaccines.
The cold chain equipment
Walk in cold room b.Deep freezer (300 ltr) and lce lined refrigerators (ILFs 300/240 ltr capacity) c.Small deep freezers and ILR ( 140/ltr) d.Cold boxes e.Vaccine carriers f.Day carriers g.Ice packs
The most important areas for maintenance cold chain are :
•Airport •Central store •Regional storage •District hospital •PHC •HP •PHC outreach clinic
Cold box
•Cold boxes are supplied to all peripheral centres. •It is mainly for transportation of the vaccines. •Before the vaccines are placed in the cold boxes, frozen ice packs are placed at the bottom and sides. •The vaccines are first kept in cartoons or polythene bags. •The vials of DPT, DT, TT and diluents should not be placed in direct contact with the frozen ice packs. •The carrier should be closely tightly.
The vital element in successful cold chain are:
•Cold chain equipments •Transportation •Trained human resources for maintaining the link
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.
Small deep freezers and ILR (140/Itr)
•One set of small deep freezers are provided to PHCs, Urban Family Planning centers and Postpartum Centres. •Deep freezers are to prepare frozen ice packs which are used in cold boxes, vaccine carriers for transportation of vaccines and during the sessions. •All vaccines at PHC level are stored in the ILR. •Vaccines like TT, DPT, DT and diluents are kept in the basket provided with the ILR. •These vaccines are never to be kept on the floor of the ILR as they may freeze and get spoiled. •A dial thermometer should be kept in the ILR and temperature recorded twice a day. •In case of equipment failure or electric supply failure, vaccines should be transferred to ice boxes and then to alternate vaccine storage.
Ice packs
•The ice packs contain water and no salt should be added to it. •The water should be filled up to the level marked on the side. If there is any leakage such ice packs should be discarded. •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 must be supplied on the day of use.
Process of maintaining cold chain
•The vaccines come in a special container to the airport. •From the airport the vaccines must be collected quickly. •They must be stored at the correct cold temperature in the refrigerator at the central store, the regional store and hospital. •They must be kept in cold during transport from one store to another. •All the vaccines must be kept at correct cold temperature in health center refrigerator. •If you need to take the vaccine to immunization camp, they should be in a vaccine carrier with ice. •During immunization session the vaccine, to be used should be in an ice bottle or a cup of ice or over the ice pack. •The vaccines like BCG, measles are stored in the coldest place.
Walk in cold room
•They are located at regional level, meant to store vaccines up to 3 months and serve 4-5 district. •Central cold room of Nepal: Teku •Regional cold room: Western: Butwal Mid-western: Surkhet Far-western: Dipayal Eastern: Biratnagar
Vaccine carriers
•Vaccine carriers are used to carry small quantities of vaccines (16-20 vials) for the out of reach sessions. •A fully frozen ice packs are used for lining the sides, and vials of DPT, DT, TT and diluents should not be placed in direct contact with frozen ice packs. •The carriers should be closed tightly.
Important of cold chain
•Vaccines are sensitive biological products which may become less effective, or even destroyed when exposed to temperatures outside the recommended range. •Cold-sensitive vaccines experience an immediate loss of potency following freezing. •Vaccines exposed to temperature above the recommended temperature range experience some loss of potency with each episode of exposure. •Repetitive exposure to heat episodes results in a cumulative loss of potency that is not reversible. •Ensuring maximum benefit from immunization.