A group from Division of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA, etc. has reported about inpatient clinical outcome of SARS-CoV-2 variants including Omicron.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8820675/
Although unvaccinated patients hospitalized with Omicron variant had a lower risk of developing severe disease or death compared to those with Delta variant, the risk of severe disease or death was similar compared to SARS-CoV-2 lineages that circulated earlier in the pandemic. Among vaccinated patients, there was no difference in the risk of developing severe illness between Delta and Omicron variants once patients were hospitalized.
In concrete terms,
Among unvaccinated patients,
The percentages of developing severe disease or death within 14 days of hospitalization were (27%) ancestral, (31%) Alpha, (32%) Delta, (26%) Omicron, and (26%) other variants.
The relative risk of developing severe disease or death within 14 days for Delta variant compared to ancestral lineages was 1.34. Compared to Delta variant, the 14-day relative risk of severe disease or death for Omicron was 0.78 and compared to ancestral lineages was 1.04 (almost the same).
Among vaccinated patients,
The adjusted hazard ratio developing the 14-day risk of severe disease or death of inpatients who were vaccinated was 0.46 (almost half) compared to unvaccinated inpatients. Severe outcomes were less common in vaccinated patients, but there was no difference between Delta and Omicron infections.