To add to my original question, is the furin cleavage site further adapted in the Omicron variant, explaining its increased infectiousness? If so, what is the difference between that and the Delta variant?
The Omicron variant is actual prior to Delta variant and prior to all other variants even so named Alpha variant. This article indicates why Omicron could be yet another lab leak.
https://bprice.substack.com/p/lab-leak-20