Objective:To analyze the clinical characteristics and prognosis of patients infected with novel coronavirus Omicron variant in Shanghai, as to provide a reference for epidemic prevention, clinical diagnosis, and treatment.Methods:Altogether 4 264 novel coronavirus Omicron variant-infected patients with positive results of nucleic acid admitted to Shanghai New International Expo Center N3 Mobile Cabin Hospital from April 2 to May 7, 2022, were included. The demographic and baseline clinical characteristics, treatment strategy, prognosis, and different factors affecting the length of hospital stay were analyzed.Results:A total of 4 264 novel coronavirus variant Omicron-infected cases were collected, including 3 111 cases (73.0%) asymptomatic infections and 1 153 cases (27.0%) mild infections. The overall median age was 45 (33, 55) years old with a range from 2 years old to 81 years old. The male to female ratio was 1.37∶1. Altogether 3 305 cases (77.5%) had been vaccinated, of which 3 166 cases completed more than 2 doses. The upper respiratory tract symptoms such as cough and expectoration were the most common clinical manifestations of these infected patients. During the course of the disease, patients with asymptomatic infection were mainly treated with traditional Chinese medicine (TCM, 55.1%) and clinical observation (36.8%), and those with mild infection were mainly treated with TCM (42.2%) or integrated Chinese and Western medicine (30.4%). All patients were cured and discharged. The overall median length of hospital stay and the negative conversion time of nucleic acid were 9 (6, 10) days and 8 (5, 9) days, respectively. Compared with the asymptomatic infected patients, the hospitalization duration and the nucleic acid negative conversion time of the mildly infected patients were slightly longer [days: 10 (8, 11) vs. 9 (5, 10); 8 (6, 10) vs. 7 (4, 9), both P < 0.001]. Multiple linear regression analysis showed that the increasing age and mild infection were associated with longer hospitalization duration, and the treatment of TCM or integrated Chinese and Western medicine was associated with shortened length of hospital stay (all P < 0.05). Conclusions:The current novel coronavirus Omicron variant epidemic in Shanghai mainly caused asymptomatic and mild infections. The young and middle-aged population had a relatively high infection rate. The upper respiratory tract symptoms such as cough and expectoration were the most common clinical symptoms. Elderly and confirmed patients had prolonged hospitalization duration, while for patients receiving TCM treatment, the hospitalization duration was shortened.