The Great East Japan Earthquake (GEJE) and subsequent tsunamis that occurred in 2011 caused extensive and severe structural damage and interrupted numerous research activities; however, the majority of such activities have been revived, and further public health researches and activities have started to follow the population affected by the disaster. In this mini-review, we overview our recent activities regarding epidemiologic studies in Miyagi Prefecture, the region most affected by the GEJE. Through our study processes, we were able to identify the particular characteristics of vulnerable populations, and provide ideas that may help save lives and reduce the amount of damage caused by a future disaster. Long-term follow-up and care of survivors is essential in affected areas, and health professionals should pay particular attention to various diseases, e.g., cardiovascular complications and mental disorders. Furthermore, building up resilience and social relationships in the community is beneficial to survivors. Ongoing cohort studies conducted before disasters can help minimize biases regarding the survivors’ pre-disaster information, and emerging cohort studies after disasters can find potential helpful novel indices. To identify characteristics of vulnerable populations, save lives, and reduce the amount of damage caused by a future disaster, constant research that is consistently improved by new data needs to be performed.