The Covid-19 pandemic affected Brazil with severity. Brazil is a large country characterized by significant socioeconomic inequalities among its regions. This study aimed to check the sociodemographic factors associated with the Covid-19 mortality rate in Brazilian municipalities. This paper is an ecological study that analyzed data of the first three death waves, with Brazilian municipalities as a unit of analysis. Municipalities were clusterized based on their vulnerabilities in the face of Covid-19. The results show that, from the second death wave in the country, the municipalities with lower social vulnerability were more likely to have a higher mortality level than the other municipalities. The results also show that, among the attributes analyzed, the urban population percentage was the one that most strongly contributed to a municipality being more likely to have a higher level of mortality. Finally, this work demonstrated that using municipality clustering contributes to a more thoughtful and accurate analysis of correlations in ecological studies.