>>A quick google found this published a week later and it looks like natural immunity to prior strains doesn't protect against Omicron.
>>https://www.cuimc.columbia.edu/news/new-study-adds-more-evidence-omicron-immune-evasion

Just for completeness, the paper published in Nature describes omicron "antibody evasion" meaning it can bypass human antibody immunity. That's predictable for current C19 vaccines that provoke an antibody response to a C19 spike protein that omicron has mutated repeatedly- but natural immunity involves more than just antibodies, such as T-cell immunity that some say is more important than antibodies against covidae.

Certainly traditional vaccines that present the entire killed or attenuated bug provoke more than an antibody response to one protein; there are a number of upcoming C19 candidates including Nuvaxovid/Covovax that has just been approved by WHO, but also several other promising candidates in trials.

IMHO latest news from South Africa is encouraging: granted, South Africa has a much younger more vigorous population than decadent western nations so findings may change as omicron pushes delta aside in the West, but so far omicron appears to spread readily but to cause less illness, even in their mostly unvaccinated population.