Comparative evaluation of severity of COVID-19 pneumonia on computed tomography of the chest in vaccinated and non-vaccinated individuals: an observational study.

Purpose: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel virus causing an infectious disease, coronavirus disease 2019 (COVID-19). Computed tomography (CT) of the chest plays a significant role in the diagnosis and prognosis of COVID-19 using computed tomography severity scoring (CT-SS). Numerous vaccines are being made available in the world to lessen the effect of the COVID-19 pandemic. The purpose of the current study is to compare the severity of COVID-19 pneumonia using CT-SS in COVID-19-positive vaccinated (Covishield/Oxford-AstraZeneca) and non-vaccinated individuals and to compare the final outcome wherever possible.

Material and methods: This observational study was carried out from March 2021 to April 2021. Forty vaccinated and 40 non-vaccinated RT-PCR-positive COVID-19 patients who underwent CT chest during the 4-12^th day of illness formed the material of the study. Semi-quantitative scoring was used, and CT-SS was calculated based on the extent of lobar involvement in all the patients. CT-SS was then compared between the vaccinated and non-vaccinated groups and the results analysed.

Results: CT scans were performed in 80 patients (40 patients each in the vaccinated and non-vaccinated groups). The majority of patients in the vaccinated group had mild (42.5%) and moderate (37.5%) CT-SS while the majority of patients in the non-vaccinated group had moderate (52.5%) and severe (27.5%) CT-SS score on chest CT. Also, no mortality was observed in the vaccinated group, with 2 deaths in the non-vaccinated group.

Conclusions: Covishield vaccine administration reduces the severity of COVID-19 pneumonia as compared to the nonvaccinated group, with a marked reduction in mortality.