Ice-packs are flat, rectangular plastic bottles filled with water and then either kept at refrigerator temperature (Figure 6.3 above), or frozen and then conditioned for use in vaccine carriers and cold boxes (Figure 6.4a). The number of ice-packs required for a cold box or vaccine carrier varies.
Every Health Post should have a minimum of two sets of ice-packs for each of their cold boxes and vaccine carriers, one in the process of being frozen or refrigerated, and the other conditioned for use in a cold box or vaccine carrier.
The proper freezing and conditioning of ice-packs is essential for maintaining the potency of vaccines. To freeze ice-packs, follow the steps in Box 6.1.
Box 6.1 Freezing ice-packs
- Fill the ice-packs with water, leaving about 20% air space at the top, and put the cap on tightly.
- Hold each ice-pack upside down and squeeze it to make sure it does not leak.
- Put the ice-packs upright in the freezer compartment of the refrigerator, so that the surface of each ice-pack is touching the evaporator plate, and close the door.
- Leave ice-packs in the freezer for at least 24 hours to freeze solid. After 24 hours they should be ready to use.
- After each vaccination session put the melted ice-packs back in the freezer as soon as possible.
Keep extra unfrozen ice-packs that do not fit in the freezer in the bottom part of the main refrigerator compartment (look back at Figure 6.3). This helps the water in these chilled ice-packs to freeze relatively quickly when you put them into the freezer, and it also helps to keep this section of the refrigerator cold in case of a power failure.
Conditioned ice-packs and chilled water packs
Conditioned ice-packs have first been fully frozen, and then removed from the freezer and left at room temperature for a short time (it may take over 30 minutes if the room is cold). Allow the frozen ice-packs to sit at room temperature until the ice begins to melt and water starts to form. Check to see if each ice-pack has been conditioned properly by shaking it and listening for the sound of water moving inside. This prevents the ice-packs from freezing the vaccines inside a cold box or vaccine carrier, and damaging the freeze-sensitive vaccines.
Studies conducted in many countries on cold chain temperatures have revealed that many vaccines are damaged more severely by freezing than by heat. So it is crucial to use properly conditioned ice-packs or chilled water packs when transporting freeze-sensitive vaccines like pentavalent, PCV10 and TT. Chilled water packs can be made by almost filling the ice-pack containers or ordinary plastic water bottles with water and placing them in the main compartment of the refrigerator for about 24 hours. Using chilled water packs may be more efficient than using conditioned ice-packs, because it takes more electricity, gas or kerosene, and more time, to freeze ice-packs and then condition them. Also, there is a risk that if frozen ice-packs are not conditioned properly, they may expose freeze-sensitive vaccines to damage from freezing during transport in vaccine carriers or cold boxes.