What is it?
The "cold chain" is a system of storage and transport of vaccines at low temperatures from the manufacturer to the actual vaccination site.
What is the need?
The cold chain system is necessary because
- Vaccine failure may occur due to failure to store and
- Transport under strict temperature controls
This is of concern because of the fairly frequent reports of vaccine-preventable disease occurrence in populations thought to have been well immunized.
The success of a national immunization program is highly dependent on a supply chain system for the delivery of vaccines and equipment, with a functional system that meets
6 rights of the supply chain -
- The right vaccine
- In the right quantity
- At the right place
- At the right time
- In the right conditions (no temperature breaks in the cold chain) and
- At the right cost
Temperature requirements for vaccines:
- Vaccines are sensitive biological products. Some vaccines are sensitive to freezing, some to heat, and others to light.
- Vaccine potency, meaning its ability to adequately protect the vaccinated patient, can diminish when the vaccine is exposed to inappropriate temperatures.
- Once lost, vaccine potency cannot be regained.
- To maintain quality, vaccines must be protected from temperature extremes. Vaccine quality is maintained using a cold chain that meets specific temperature requirements.
- All those who handle vaccines and diluents must know the temperature sensitivities and the recommended storage temperature for all the vaccines in the national schedule.
Sensitivity to heat and freezing:
The vaccines are grouped into six categories.
- Within each of these six categories, the vaccines are arranged in alphabetical order, not in order of sensitivity to heat, within the group.
- The most heat-sensitive vaccines are in group A and the least heat-sensitive vaccines are in group F.
- The heat stability information shown for freeze-dried vaccines applies only to unopened vials;
- Most freeze-dried vaccines rapidly lose potency after reconstitution.
It is important to keep opened multi-dose vaccine
vials (that do not contain preservatives - whether lyophilized
or liquid) - cooled at a temperature between +2°C and +8°C
during the immunization session, or used within 4 hours
after opening, whichever comes first.
Vaccines that are sensitive to freezing and should be
protected from sub-zero temperature are:
-
- Cholera
- DTaP-hepatitis B-Hib-lPV (hexavalent)
- DTwP or DTwP-hepatitis B-Hib (pentavalent)
- Hepatitis B (Hep B)
- Hib (liquid)
- Human papillomavirus (HPV)
- Inactivated poliovirus (IPV)
- Influenza
- Pneumococcal
- Tetanus, OT, Td
- Rotavirus (liquid and freeze-dried)
Sensitivity to light:
Some vaccines are very sensitive to light and lose
potency when exposed to it. Such vaccines should always be
protected against sunlight and strong artificial light.
Vaccines
sensitive to light are:
- BCG,
- Measles,
- Measles-rubella,
- Measles-mumps-rubella, and
- Rubella.
These vaccines are
supplied in dark glass vials that give them some protection,
but they should be kept in their secondary packaging for as
long as possible during storage and transportation.
At the health facility level (usually health centers and
health posts), health workers can adequately protect
vaccines by doing the following :
- Keep vaccines in appropriate vaccine refrigeration equipment;
- Use a temperature monitoring device to ensure temperatures remain between +2°C and +8°C;
- Transport vaccines to immunization sessions in a vaccine carrier, correctly packed, using coolant packs that have been properly prepared; and
- During immunization sessions, fit a foam pad (if available) at the top of the vaccine carrier.
At the health facility, one person must have overall
responsibility for managing the vaccine cold chain. A second
person can fill in when the primary person is absent. Their
responsibilities should include :
- Checking and recording vaccine temperatures twice daily; typically in the morning and at the end of the session or day;
- Properly storing vaccines, diluents, and water packs; and
- Handling preventive maintenance of cold chain equipment.
All health workers in a facility should know how to
monitor the cold chain and what to do if the temperature is out
of range.
Electrical Cold Chain Equipment:
There is equipment of different capacities for the storage of
vaccines at different levels, which are dependent on an electric
supply to maintain the recommended temperature.
1. Walk-in-freezers {WIF):
The Walk-in-freezer is a pre-fabricated modular
polyurethane foam (PUF) insulated panel assembled cold
room with two identical refrigeration units and a standby
generator set to provide an uninterrupted power supply.
- The generator set starts automatically as soon as the power cuts off.
- It maintains a temperature between - 15°C to - 25°C.
- WIF is usually installed at national, state, and regional vaccine stores.
- It is used for bulk storage of OPV vaccine and for preparation of frozen ice packs for vaccine transportation.
2. Walk-in-coolers {WIC):
The walk-in cooler is a pre-fabricated modular
polyurethane (PUF) insulated panel assembled cold room.
- They maintain a temperature of +2°C to +8°C.
- In India, under UIP usually WIC with capacities of 16.5, 32 and 40 Cubic meters are in use.
- These are used for the storage of large quantities of all UIP vaccines like BCG, hepatitis B, DPT, pentavalent, IPV, measles, and TT.
- They have two identical cooling units and a standby generator with automatic start and stop functions.
- These Walk-in-coolers are installed at government medical store depots, and state, and regional vaccine stores.
- The WICs have been installed in some district vaccine stores based on the target beneficiary and requirement.
WIC and WIF come with a continuous temperature
recorder and alarm system. Once the temperature of WIC/
WIF exceeds the recommended storage temperature the
alarm system gives an alarm loudly.
3. Deep freezer (DF):
The Deep freezer is equipment, which operates on a
vapor compression system similar to any conventional type
of refrigerator operating on 220 volts A.C. mains supply.
- However, DF has a top opening lid to prevent loss of cold air during door opening. The cabinet temperature is maintained between -15° to - 25°C.
- This is used for storing OPV vaccine for 3 months (district level and above only) and also for freezing ice packs (at sub-district level only).
- Unlike the ice-lined refrigerator (ILR), the DF has little or limited hold-over time which is dependent on the number of frozen ice packs in it and the frequency of opening.
- These are available in different sizes.
- The DF which is used for storing vaccines should not be used for the preparation of icepacks, as it may increase the cabinet temperature and can be potentially harmful to the vaccines (OPV).
However adequate frozen icepacks can be
kept permanently inside the vaccine storing DF for
increasing the hold-over time.
4. lce lined refrigerator {/LR):
One of the most important links in the cold chain is ice
ice-lined refrigerator (!LR).
This is equipment that operates
on a vapor compression system similar to any conventional
type of refrigerator operating on 220 volts A.C. mains
supply.
- ILRs are to maintain a cabinet temperature between +2°C to + 8°C and are used to store vaccines at district and sub-district levels.
- These types of refrigerators are top openings because they can hold the cold air inside better than a refrigerator with a front opening.
- It can keep vaccines safe with a minimum of 8 hours of continuous electricity supply in 24 hours.
- The ILRs are categorized based on vaccine storage capacity.
- These are available in different sizes. Usually, the larger ILR is supplied to district headquarters and the smaller ILR to PHC headquarters, based on the size and population.
- Inside the ILR there is a lining of water containers (ice packs or tubes) fitted all around the walls and held in place by a frame.
- When the refrigerator is functioning the water in the containers freezes and cools the cabinet.
- When the electricity supply fails, the ice lining maintains the inside temperature of the refrigerator at a safe level for vaccines.
- Therefore, the temperature is maintained in ILR for a much longer duration than in deep freezers and domestic refrigerators.
- Thus ILR is an ideal option for safe storage of vaccines.
- Based on the temperature zone, the inside of the ILR can be divided into 2 parts, the upper part, and the lower part.
- In most of the ILR models, the lower part is cooler compared to the upper part, as the cooler air is heavier and settles down at the bottom of ILR.
- Hence upper part is the preferred location for storing the freeze-sensitive vaccines.
Where to keep the vaccines:
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 the bottom of the basket
- while DPT, TT, hep B, IPV, and pentavalent vaccines and diluents are kept in the upper part of the basket.
- These vaccines should never be kept directly on the floor of the refrigerator as they can freeze and get damaged.
- In case a basket is not available, two layers of empty ice packs can be laid flat on the bottom of the ILR.
Hold-over time of the equipment:
In the event of power failure, hold-over time is defined as
- "the time taken by the equipment to raise the inside cabinet temperature from its temperature at the time of power cut, to the maximum temperature limit of its recommended range."
- For example, in the case of ILR if the cabinet temperature is +4°C at the time of power-cut, then the time taken to reach +8°C from +4°C will be hold-over time for that ILR.
- Hold-over time depends on the following factors :
- Ambient temperature: More the ambient temperature less the hold-over time;
- Frequency of opening of the lid and use of basket;
- Quantity of vaccines kept inside with adequate space between the containers (Equipment empty/ loaded); and
- Condition of the ice-pack lining (Frozen/ partially frozen/melted)
5. Domestic refrigerator (front load refrigerator):
Domestic refrigerators can also maintain the cabinet
temperature between +2°C to +8°C, but the hold-over time
and capacity to store vaccines/freeze icepacks is limited.
They can be used for storage of vaccines at private clinics
and nursing homes, provided continuous power supply is
ensured.
Load a domestic refrigerator as follows:
- Freeze and store ice packs in the freezer compartment, they should be kept vertically to avoid leaking with a space of at least 2 mm. Ice packs should be taken out from the left;
- All the vaccines and diluents should be stored in the refrigerator compartment.
- Arrange the boxes of vaccines in stacks so air can pass between them.
- Placement of vaccines in the refrigerator with freezer on top is as follows:
- measles, BCG, rotavirus vaccine, and OPV on the top shelf.
- DPT, pentavalent vaccine, TT, IPV, hepatitis B, and JE vaccine on the middle shelf, and diluents next to the vaccine with which they are supplied;
- Keep ice packs filled with water on the bottom shelf and at the door of the refrigerator.
- They help to maintain the temperature in case of power-cut, and
- Closer expiry date vaccines should be kept in front.
- A dial thermometer should be kept in the ILR and temperature recorded twice a day.
- At the time of defrosting the vaccines are shifted to the cold boxes containing the required number of frozen ice packs.
- In case of equipment failure or electric supply failure, vaccines should be transferred to ice boxes and then to alternate vaccine storage.
DOs and DONTs for the use of ILR/ freezer.
D0s:
- Keep the equipment in a cool room away from direct sunlight and at least 10 cm away from the wall;
- Keep the equipment leveled;
- fix the equipment through a voltage stabilizer;
- keep vaccines neatly with space between the stacks for circulation of air;
- Keep the equipment locked and open only when necessary;
- defrost periodically, supervise the temperature record; and
- If vaccines are kept in cartons, make holes on the sides of the cartons for cold air circulation.
DONTs:
- do not keep any object on these equipments;
- Do not store any other drug;
- Do not keep drinking water or food in them;
- Do not keep more than one month's requirements at the PHC level, and
- Do not keep date expired vaccines.
To be on the safe side, write the time of reconstitution on the label of
these vaccine vials and discard them after 4 hours (2 hours
for JE vaccine).
Do not keep any used vials in the cold chain.
Return the unused vaccine vials from the session site to
the PHC on the same day in the cold chain through
alternative vaccine delivery.
Keep the box labeled
"returned unused" in the ILR for all unused vaccines that
can be used in the subsequent session, but discard vaccines
that have been returned unopened more than three times.
6. Cold boxes:
Cold boxes are supplied to all peripheral centers.
- These are used mainly for transportation of the vaccines.
- 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.
- The vials of DPT, OT, TT, vaccines, and diluents should not be placed in direct contact with the frozen ice packs.
7. Vaccine carriers:
- Vaccine carriers carry small quantities of vaccines ( 16-20 vials) for the out-of-reach sessions.
- 4 fully frozen ice packs are used for lining the sides, and vials of DPT, OT, TT, and diluents should not be placed in direct contact with frozen ice packs.
- The carriers should be closed tightly.
8 . Day carriers:
Day carriers 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 a few hours. 9. 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 the sub-center and village level.
- For this reason, vaccines are not stored at the sub-center level and must be supplied on the day of use.
Solar cold chain equipment:
Solar systems used in UIP are mainly of two types.
1. Solar refrigerator battery drive.
2. Solar refrigerators direct drive.
1. Solar refrigerator battery drive:
A solar refrigerator operates on the same principle as a normal compression refrigerator but incorporates low voltage
(12 or 24V) DC compressors in place of mains AC voltage-operated compressors.
- The battery is charged with solar energy.
- A solar refrigerator has good PUF insulation around the storage compartments to maximize energy efficiency.
- Battery, charge controller, and solar panels are the major additional components associated with solar refrigerators.
Vaccine refrigerator/freezer:
It is a refrigerator cum freezer having a basket for storing of
vaccine and freezing of ice-packs. It has two separate
compartments:
1. Vaccine storage compartment maintains a temperature
range of + 2°C to + 8°C.
2. The Freezer compartment is for storing frozen ice packs maintaining temperatures up to -7°C.
- For each refrigerator and freezer compartment, it has a separate DC compressor. The refrigerator is designed for continuous operation, therefore an ON/OFF switch is not provided, as it is not necessary.
- The freezer, however, does have an ON/OFF switch to allow for defrosting. during the night and on cloudy days.
- These refrigerators are wired directly to the photovoltaic generators.
