While severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) continues to spread rapidly worldwide, some issues such as the uncertainty of the disease progress, whether intensive care will be needed, and risk classification are still important for clinicians. It is notable that in countries where latent tuberculosis infection (LTBI) is common and participating in the national Bacillus Calmette-Guerin (BCG) vaccination program, the case-fatality rates are relatively low throughout the world. In this study, it was aimed to evaluate the effects of the BCG vaccine and LTBI status on the course of the disease in patients diagnosed with coronavirus-19 (COVID-19) infection and to compare the LTBI rate with people with and without COVID-19 infection. The patients diagnosed with COVID-19 infection who were hospitalized during a period of seven months between May 1st to December 1st, 2020 were investigated by the QuantiFERON-TB Gold Plus (QFT-Plus) test in the blood samples for the presence of LTBI. For the comparison of the patients diagnosed with COVID-19 and people without COVID-19 infections in terms of LTBI rate retrospectively; all consecutive patients who were sent blood samples to the mycobacteriology laboratory for the QFT-Plus test between January 2016 and December 2019 were included in the study. Demographic, clinical, radiological, laboratory, and follow-up data of the patients were obtained from the electronic patient file. A total of 170 patients (n= 9 8 male [57.6%], n= 72 female [42.3%], mean age= 53.5 ± 15.8 years) were enrolled. Twenty-five patients' (25/170 [14.7%]) QFT-plus tests were positive. When the cases with positive QFT-Plus test (n= 25) and the cases with negative QFT-Plus test (n = 145) were compared in terms of disease severity respectively; it was determined that mild/moderate patients were 18/25 (72%) and 108/145 (74.5%), severe patients were 7/25 (28%) and 37/145 (25.5%) (p= 0.988). When these two groups were compared in terms of the clinical course respectively; the need for intensive care was 6/25 (24%) and 34/145 (23.4%) (p= 1.00), oxygen therapy requirement was 13/25 (52%) and 49/145 (33.8%) (p= 0.128), and death was 5/25 (20%) and 18/145 (12.4%) (p= 0.341). QFT-Plus positivity was 25/170 (14.7%) in patients diagnosed with COVID-19, while in control group it was 198/496 (39.9%) (OR= 0.259, 95% CI [0.164-0.411], p<0.001). When the values were evaluated quantitatively, in the COVID-19 patient group, QFT-Plus T1/T2 (IU/ml) interferon (IFN)-ɣ was 0.87 ± 1.52/0.62 ± 1.53, while in the control group it was 1.52 ± 3.69/1.50 ± 3.33 (p= 0.032, p= 0.04). There was no significant difference in the parameters investigated between 82 (48.2%) patients with BCG vaccine and those 88 (51.8%) without BCG vaccine. Although it was not statistically significant in our study, increased oxygen therapy requirement and higher mortality rates in the QFT-Plus positive group were remarkable. The detection of statistically significantly lower LTBI rates and T1-T2/IFN-ɣ values in the COVID-19 group supported that SARS-CoV-2 infection may suppress lymphocyte functions in patients and IFN-ɣ response. We believe that the results of our study are remarkably valuable, but more clinical studies are needed to elucidate the relationship between BCG vaccine, LTBI, and COVID-19 infection.