Computed tomography (CT) is a critical tool for the diagnosis of pneumonia caused by SARS-CoV-2. The Delta and Omicron variants show distinct clinical features, but the radiological differences between pneumonia caused by these variants have not been extensively studied in patients with oxygen-dependent pneumonia.

To compare the radiological and clinical features of pneumonia in patients hospitalized with oxygen-dependent SARS-CoV-2 infection caused by the Delta and Omicron variants.

We performed a retrospective single-center study, including patients hospitalized with oxygen-dependent SARS-CoV-2 pneumonia between October 2021 and February 2022. Clinical and radiological data were collected and compared between patients infected with the Delta variant and those with the Omicron variant. CT scans were reviewed by a radiologist and a pulmonologist blinded to clinical and variant information.

A total of 135 patients with the Delta variant and 48 with the Omicron variant were included. Patients infected with Omicron were older (median age 75 years [68–83.2] vs 69 years [62–77.5], p = 0.004), more immunocompromised (52 % vs. 25 %, p < 0.001), and had higher vaccination rates (73 % vs. 51 %, p = 0.009). Radiologically, ground-glass opacities were present in 95 % of patients. There were no significant differences in the degree of lung involvement, type of lesions and their predominance. Unilateral lung involvement was more common in Omicron-infected patients (8.3 % vs 0.74 %, p = 0.02).

While Omicron oxygen-dependent pneumonia occurred in older and more comorbid patients, its clinical and radiological features were largely indistinguishable from those caused by the Delta variant, except for a higher rate of unilateral lung involvement.