Clinical comparison of omicron and delta variants in older COVID-19 patients and the effect of vaccination status

Abstract

Aim: It was aimed to investigate the clinical course of the Omicron vand Delta variant among the SARS-CoV-2 vaccinated and unvaccinated COVID-19 patients over 65 years old and to compare their effects on patients.
 Material and Method: The study was conducted on 567 COVID-19 patients over 65 years old. All patients’ gender, age, medical history, COVID-19 PCR test results, blood test results, thorax CT images, vaccination status, hospitalization status, and treatment results were recorded. When evaluating the chest CT images, a semiquantitative scoring system was used. The patients were divided into the Omicron and Delta variant subgroups, and vaccinated and unvaccinated groups. Comparisons were made between the Delta variant and Omicron variant groups, the vaccinated and unvaccinated patient groups,and SARS-CoV-2 mRNA vaccinated and inactivated SARS-CoV-2 vaccinated patient groups.
 Results: A total of 519 patients were included in the study.337 patients were in the Omicron variant group, 182 were in the Delta variant group.The hospitalization rate, ICU admission rate, mortality rate, rate of symptomatic patients,and the median thorax CT severity score was significantly higher in the Delta variant group than the Omicron variant group.The hospitalization rate, ICU admission rate, mortality rate, median thorax CT score and the rate of asymptomatic patients was significantly higher in the unvaccinated patient group than in the vaccinated group.There was no significant difference in the mortality rates and in the ICU admission rates between the inactivated SARS-CoV-2 vaccinated group and the SARS-CoV-2 mRNA vaccinated group.
 Conclusion: The SARS-CoV-2 Omicron variant compared to the Delta variant and the SARS-CoV-2 vaccinated patients compared to the unvaccinated patients had a milder clinical course and less mortality in COVID-19 patients over 65 years old.