During the COVID-19 pandemic, doctors faced an unprecedented mass admission of patients with viral atypical pneumonia. The objective of the study was to compare the clinical characteristics of the first and second waves of the pandemic. An analytical observational study was carried out on patients with COVID-19 pneumonia who were admitted to Hospital Carrión de Huancayo, Peru located at more than 3000 meters above sea level. Two study periods were determined, group one represented by the first wave characterized by massive restriction and strict quarantine and the second wave where productive activities had already normalized to a great extent. Of a total of 252 patients with COVID-19, the average age was 56 years in the first wave and 52 years in the second wave, the male sex was more frequent in both 74% and 57%, mortality was 27% and 23 %, the time of illness was 8 days and 10 days, respectively. On the other hand, the percentage of use of antibiotics, ivermectin and hydroxychloroquine was higher in the first wave. The use of corticosteroids and prolonged hospital stay was more frequent in the second wave. Comparison of both waves shows differences in age, mortality and time of illness, which may be due to the new molecular variants of SARS-COV-2.