Keeping vaccines cold in rural regions and during transport is particularly difficult when a fridge is not available. Under these circumstances, a cool box is very useful. Usually, a cool box consists of a closable polystyrene container. Frozen ice packs (they should rattle when shaken) are placed inside the cool box on the bottom and sides as well as under the lid.
Measles and polio vaccines should be placed at the bottom where it is coldest. The other vaccines can then be placed above them. Vaccines must never be allowed to freeze. Keep the top firmly on to protect the vaccines from sunlight.