It is not clear whether re-infection by SARS-CoV-2 occurs as a rare event or not, but since the start of the pandemic limited number of re-infection has been reported. This study reports the clinical presentations and comperative genome analysis of two patients who were suspected of re-infection. The patients showed mild clinical symptoms and varied antibody test results in the two episodes of infections. New generation sequencing of the isolates revealed the presence of different mutations between isolates from the previous and last infections. Therefore it is important to monitor these mutations and assess their capacity of evading previously occurred antibodies.