We retrospectively assessed the clinical status of patients with coronavirus disease 2019 (COVID-19) who were admitted to the Tokyo Saiseikai Central Hospital. Sixty-five patients were enrolled and categorized into either surge 1: patients admitted between March 20 and May 2, 2020 (n = 15) or surge 2: patients admitted between June 4 and August 31, 2020 (n = 50). Fatalities and severity were significantly lower in surge 2. Although the C-reactive protein, lactate dehydrogenase, and D-dimer tests, which are indicators of aggravation, showed a tendency to be lower in surge 2, the patients with sustained high levels of these indicators did not present clinical aggravation. An increase in cases of younger patients and those with less severity, as well as improvements in the laboratory testing system, may have improved the rates of fatality and severity. Moreover, early intervention with drug therapy against COVID-19, such as remdesivir and dexamethasone, may have contributed to the aggravation suppression in surge 2.