An evaluation of patients with a previous endemic coronavirus infection during the COVID-19 pandemic.

Few studies exist on the clinical manifestation of coronavirus disease 2019 (COVID-19) in patients who previously had a common cold due to an endemic coronavirus (eCoV). In a retrospective scan of the data obtained in our microbiology laboratory, 64 patients who were diagnosed with an eCoV infection between 2016 and 2020 were identified. National COVID-19 surveillance data showed that four (6.2%) of 64 patients were infected with severe acute respiratory syndrome coronavirus 2 by the end of 2020, while, simultaneously, the COVID-19 prevalence in the city of Malatya ranged from 7.8% (polymerase chain reaction-based diagnosis) to 9.2% (total diagnosis). The differences were found statistically significant (6.2% vs. 7.8%, p < .01; 6.2% vs. 9.2%, p < .001). Patient interviews and evaluation of medical records revealed that these four patients did not manifest any severe COVID-19 symptoms despite their substantial comorbidities, and they did not require hospitalization. Consequently, despite a low number of samples, we determined a lower frequency of COVID-19 among the patients who had a prior eCoV infection, and the results of this study support the previous findings that people with a prior eCoV infection develop a milder case of COVID-19. Our results may provide some insights for future studies aiming at vaccine development, but detailed investigations are still required.