Demographic characteristics of the patients
During the designated study period, Shanghai Geriatric Medical Centre admitted a total of 5524 patients who were diagnosed with SARS-CoV-2 infections. After removing subjects that did not meet inclusion criteria, the study included 3025 patients. Nirmatrelvir-ritonavir was given to 324 patients [5.8%]. The control group consisted of carefully selected 324 patients from the retrospective cohort, with baseline characteristics used as matching criteria (Figure 1). Following the matching process, patient characteristics were comparable between the nirmatrelvir-ritonavir and control cohorts at baseline, with all SMDs below 0.1, except for the duration from the initial positive PCR test to hospitalization (SMD=-0.43), RT-PCR Ct value upon admission (SMD=-0.59), administration of corticosteroids (SMD=0.11) and administration of antiviral medication (SMD=0.10). The baseline characteristics of patients treated with or without nirmatrelvir-ritonavir are displayed in Table 1. Overall, less than one-third of the group were completely immunized, with 194 individuals (29.9%) having been administered at least one dose of the SARS-CoV-2 vaccine. Most of the patients were over the age of 65, and the median age was 77 years old (interquartile range [IQR], 67-88 years). 314 (48.4%) patients were men. 547 (84.4%) were classified as mild cases. The prevalent underlying conditions consisted of individuals aged ≥65 years (530 [81.8%]), hypertension (311 [48.0%]), and diabetes (144 [22.2%]); more than one risk factor was present in 432 (66.7%) patients. There was no significant difference found between the nirmatrelvir-ritonavir and matched control groups.