Coronavirus Disease 2019 (COVID-19) is an infectious disease which is caused by a new strain of coronavirus. Older individuals and people with comorbidities have a higher risk to develop more severe illness. COVID-19 survivors will have active immunity in conjunction with increase of SARS-CoV-2 antibody (Ab) titer 2-weeks after the symptoms onset and will be lasted until 12-weeks. Therefore, it will give protection against reinfection of COVID-19. This study reports a case of COVID-19 rapid reinfection in sixty-year-old man with diabetes mellitus. Case illustration: a sixty-year-old man presented to the emergency department with fever accompanied by cough, runny nose, malaise, and metallic taste since one day before admission. There was a history of uncontrolled diabetes mellitus (DM) and COVID-19 infection 35-days before hospital admission without any symptoms. The current physical examinations demonstrated a mild dyspnea with oxygen saturation 97%, and diffuse rhonchi at the right area of chest auscultation. Chest X-ray discovered a multiple consolidation of the right lung. Fasting blood glucose (FBG) was 205 mg/dl, and 2-hour postprandial glucose was 508 mg/dl. The PCR of SARS-CoV-2 was taken and the result was positive. COVID-19 Ab titers IgM and IgG were 0.18 U/ml and 0.43 U/ml (<0.8 U/ml ? non-reactive), respectively. The patient was diagnosed with COVID-19 reinfection and DM. The patient was treated with convalescent plasma, antivirus, antibiotics, insulin, steroid, anticoagulant, and other symptomatic medications. As the results, a well improvement of his clinical condition and the increase of Ab COVID-19 IgM and IgG evaluation test after convalescent plasma administration, 0.28 AU/ml and 17.67 AU/ml, respectively, were recorded. Summary: Researches revealed that DM might cause the specific immunity system dysfunction and the low production of antibody. This study found that poor blood-glucose control with a low Ab of SARS-CoV-2 production might induce this patient to have a COVID-19 reinfection. 

Albert William Hotomo has completed his MD at the age of 24 from Atma Jaya Catholic University of Indonesia, Jakarta. He works as a general practitioner at St. Carolus Borromeus Hospital, Kupang. As his passion to learn internal medicine, he acquires as an internal medicine internship at Prof.W.Z.Johannes General Hospital. He has presented several studies with a highlight of internal medicine topic at some international medical doctor meetings. He has also taken a halve-minor about vitality and ageing at the Leids Universitair Medisch Centrum (LUMC), Netherlands, which emphasize about the biology of ageing and geriatric medicine. He has served as a medical doctor at East Nusa Tenggara since 2020.