A (preprint) study of 80,000 patients with Covid during December 2021 presenting at the Kaiser Permanente Southern California healthcare system composed a mixture of Delta (16,982) and Omicron (52,297) patients.
Hospital admissions were 222 for Delta (1.3%) and 235 for Omicron (0.5%). Rates of ICU admission among Omicron patients were one quarter that of Delta. No Omicron patients required ventilation and they had shorter hospital stays by 3.4 days (70% less than Delta).
There were 14 Delta deaths (99.92% recovered) and 1 Omicron death (99.998% recovered).
The most interesting breakdown of the study statistics is between vaccinated and unvaccinated. One half of Delta cases were unvaccinated but only 27% of Omicron cases were unvaccinated. Crucially unvaccinated individuals face an eight-fold reduced risk of infection from Omicron and a six-fold reduced risk of hospitalisation compared to Delta.
The results support the prevalent view that Omicron is a mild illness affecting the upper respiratory tract, but it is still not an illness that you would deliberately set out to catch as it can become serious in a very small number of cases.