Title: Components of the cold chain
Course: Level 3 - Immunization > Section: Cold chain, vaccine supply and stock management

How to Maintain the Correct Temperature in Cold Chain

i) Monitoring the temperature in vaccine refrigerators:

To monitor the temperature of the main section of a refrigerator you need:

- A thermometer.
- A temperature chart, which you should tape to the outside of the door.

To monitor the temperature, proceed as follows:

- Set the refrigerator thermostat during the coldest part of the day to around +2ºC to +4ºC.
- Monitor temperatures first thing in the morning and before you leave the post in the afternoon. If the temperature is between +2ºC to +8ºC, do not adjust the thermostat.
- Continue to monitor the temperature first thing in the morning and before you leave the post in the afternoon, including workdays, weekends, and holidays.
- Record the temperature for the day and time on the refrigerator temperature chart.

Keep the booklet of 12 monthly temperature recording forms on the top of each unit and check daily to see that the temperature record is maintained as given below.

Fig 4.12. Temperature monitoring chart.

Record the details about the equipment (Make, Machine Number, Functional Status, date of breakdown, Date of Intimation and Date of Restoration) in Monthly PHC Report. This will provide the information that is needed to schedule maintenance and repair and evaluate the adequacy of equipment.

ii) Maintaining the correct temperature in cold boxes and vaccine carriers:

If the ice-packs inside the cold box or vaccine carrier have completely melted:

- Discard all reconstituted vials.
- Check VVMs status and return the vaccines that can be used to a working refrigerator as soon as possible.
- If there is no VVM and the vaccine has only been exposed to warm temperatures for a few hours, return the vials to the refrigerator, place them in the "use first" box, and use them before other vials.

Remember

In order to maintain the temperature in cold boxes and vaccine carriers:

- Place the adequate number of conditioned ice packs in the cold box or vaccine carrier.
- Keep the cold box or vaccine carrier in the shade.
- Keep the lid tightly closed.
- Use the foam pad to hold vials during immunisation sessions.
- Avoid unnecessary openings.

How to Maintain Cold Chain Equipment

i) Maintaining vaccine refrigerators:

- A refrigerator works well only if it is properly installed, cleaned and defrosted regularly.
- Thick ice in the freezer compartment does not keep a refrigerator cool. Instead, it makes the refrigerator work harder and uses more power, gas or kerosene. You should defrost the refrigerator when ice becomes more than 0.5 cm thick, or once a month, whichever comes first.

ii) To defrost and clean a refrigerator:

- Take out all the most heat-sensitive vaccines (OPV, Measles, BCG) and transfer them to a cold box lined with frozen ice-packs.
- Take out all the freeze-sensitive vaccines (DPT-HepB-Hib, PCV, TT, Rotarix) and diluents, and transfer them to a cold box lined with conditioned ice-packs.
- Turn off the power supply to the refrigerator.
- Leave the door open and wait for the ice to melt. Do not try to remove the ice with a knife or ice pick, since doing so can permanently damage the refrigerator. You can place a pan of boiling water inside and close the door.
- Clean the inside of the refrigerator and door seal with a clean wet cloth.
- Turn the refrigerator on again.
- When the temperature in the main section falls to +8°C or lower (but not less than +2°C), return the vaccines, diluents, and ice-packs to their appropriate places.
- If you need to defrost your refrigerator more than once a month, it could be because:

- You may be opening it too often (more than three times daily); or
- The door may not be closing properly; or
- The door seal may need to be replaced.

iii) What to do when a vaccine refrigerator is out of order:

- If your vaccine refrigerator stops working, first protect the vaccines and then repair the refrigerator.

iv) Protecting the vaccines:

- Move the vaccines to another place until the refrigerator is repaired. If you think that the problem will last only a short time, you may use a cold box or vaccine carrier lined with conditioned ice-packs for temporary storage. For a longer duration, use another refrigerator. Always keep a freezer indicator with the freeze-sensitive vaccines to monitor eventual freezing.

v) Restoring the refrigerator to working order:

- Check the power, gas or kerosene supply. If there is no power, make other arrangements (e.g. store the vaccine in a household refrigerator) until power is restored. If there is no gas or kerosene, get it as soon as possible.
- If a lack of power, gas or kerosene is not the problem, repair the refrigerator or report to your repair technician or supervisor.
- Record the breakdown on the daily temperature recording chart.
- Note: Concerning the routine maintenance and the servicing of refrigerators, WHO technical manual exist for each kind of refrigerator.

vi) Maintaining cold boxes and vaccine carriers:

- Vaccine carriers and cold boxes must be well dried after their use. If they are left wet with their lids closed, they will become mouldy. Mould may affect the seal of the cold boxes and vaccine carriers. If possible, store cold boxes and vaccine carriers with the lid open, when not being used.
- Knocks and sunlight can cause cracks in the walls and lids of cold boxes and vaccine carriers. If this happens the vaccines inside will be exposed to heat.
- If a cold box or vaccine carrier wall has a small crack you may be able to repair it with adhesive tape until you can get an undamaged one.