In the era of a health crisis of international concern, the authorities must elaborate on communication strategies to inform the right way about the risks and how to deal with them. In this regard, we analyze the feedback on the used communication strategies in Algeria during the Covid-19 outbreak, to identify the most impactful ones and characterize the population sensitivities. To this end, Computer Assisted Personal Interviews (CAPI) were conducted among 1500 households to collect the data. Videos and posters concerning Covid-19 information were shown to the inteviewees. Then a method inspired by that of Elimination and Choice Expressing REality is used to select the most impactful messages. Moreover, statistical models are used to identify the corresponding message to each target population. The obtained results show that videos containing real images or those with celebrities are the most impactful. In particular, to target youth (under 25), urban people, and those living in small household sizes. Videos are judged as more impactful than posters, and videos with real images are better than schematic ones. Empathy and guilt seem to play a role in the communication messages that impact the youth, and people with less than basic educational level. Furthermore, the evolution of the media explains why the elderly gave a better ranking to posters with writing, whereas the youth were more impacted by the audio-visual messages. In sum, to sensitize Algerians the government must focus on messages that contain real images, or famous people having good credibility. Unfortunately, until now, the videos using schemes are more deployed in Algeria, even those established by the World Health Organization.