Universal health coverage is high up the international agenda. The majority of the West Africa's countries are seeking to define the content of their compulsory, contribution-based medical insurance system. However, very few countries apart from Mali have decided to develop a national policy for poorest population that is not based on contributions. This qualitative research examines the historical process that has permitted the emergence of this public policy. The research shows that the process has been very long, chaotic and suspended for long periods. One of the biggest challenges has been that of intersectoriality and the social construction of the poorest to be targeted by this public policy, as institutional tensions have evolved in accordance with the political issues linked to social protection. Eventually, the medical assistance scheme for the poorest saw the light of day in 2011, funded entirely by the government. Its emergence would appear to be attributable not so much to any new concern for the poorest in society but rather to a desire to give the social protection policy engaged in a guarantee of universality. This policy nonetheless remains an innovation within French-speaking West Africa.