Vaccine carriers are insulated containers that, when lined with coolant packs, keep vaccines and diluents cold during transportation. They are smaller than cold boxes and are easier to carry when walking. They are used for transporting vaccines from health facilities with refrigeration to outreach sessions where refrigeration and ice are not available. They are typically carried by a single health worker travelling on foot or by other means, where the combined journey time and immunization activity ranges from a few hours to a whole day. The vaccine storage capacity of vaccine carriers are between 0.1 and 5.0 litres.