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This may not mean Omicron is less severe itself. It may just be indicative of 70-80% of populations being prior infected or vaccinated like South Africa was. Unvaccinated individuals still have a tough time clearing this.

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Have you seen any solid data about how unvaccinated individuals fare with omicron? I have been curious and it’s been hard to come by.

This preprint from yesterday suggests basically what you’re saying, that underestimated prior immunity could possibly be a confounding factor in the models used to assess relative severity. But even that is still unclear at present

https://doi.org/10.1101/2021.12.21.21268116

Edit: table 3 in the imperial college preprint addresses this, they estimate hazard ratio of like 0.6-0.7 for unvaccinated, relative to delta

That's exactly the conflating factor that worries me. We know Omicron is much better at evading prior immunity, so we should expect a higher proportion of people with prior immunity among Omicron infections, which (all other things being equal) will make Omicron look less severe. But this would be illusory - the absolute number of severe infections wouldn't be less, they would just be diluted by mild infections that otherwise wouldn't have happened at all.

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