"The DRC has difficulties on a number of levels. The country has such a high birth rate — 3.5 million children are born each year — that it needs to conduct mass vaccination campaigns every two years. Those campaigns, in which tens of thousands of health workers fan out across this vast country, are a logistical nightmare. First, the government has to get the vaccine from the capital, Kinshasa, to remote villages that can be reached only by helicopter — or through bloody conflict zones in the eastern part of the country. The vaccine must be kept between 2 °C and 8 °C from the time it leaves the warehouse until it is administered — a challenge in a tropical environment where power outages are frequent. Health workers must be trained to inject it safely, a much more difficult task than dropping liquid polio vaccine on a child’s tongue. The vaccine comes as a powder, which must be reconstituted with an accompanying solution of sterile diluent and then used within 6 hours. It also comes in ten-dose vials; worried about wastage, vaccinators are sometimes hesitant to open one when just a few children show up to a session, so the children go unimmunized."