Abstract Background:Diphtheria is a lethal disease caused by a type of microorganism from a group of bacteria called Corynebacterium diphtheria. In 2015, 1 case was found, and one died, in 2016, there were 8 cases, and one died, and in 2017, there were 36 cases, and 2 children died. Aims:The purpose of this study is to analyze the extraordinary causes of diphtheria cases continue to increase despite good basic immunization coverage. Methods:This study used the literature review that was obtained from various sources, namely Google Search, Google Scholar, Sciencedirect.com, E-book, and SAGA Journal, Scientific Work with the keywords of immunization and diphtheria from 2015-2019. Results: From the results of observations on the physical environmental conditions of the house carried out by chi-square statistical tests, the significance of 0.008 or p-value was <0.05 (p <α) [6]. The results of statistical analysis using multiple linear regression showed a significance value of 0.01, indicating that there was an effect of population density (p <0.05) (2) Conclusion: It can be concluded that the cause of diphtheria outbreaks in Sampang District is independent of basic immunization coverage, including (1) poor vaccine management, (2) inadequate physical environment of the house, and (3) population density.Therefore, further and more detailed research is to be carried out.