I’m in New York City and there’s lots of people getting Omicron. In my experience:
Vaxxed people can (and mostly do) get omicron — whether they had a booster or not, and whether they also had Alpha or not.
I don’t know any unvaxxed people who had Alpha so I don’t know if they are also getting Omicron but if I had to guess I’d say yes.
People who had Delta, whether they were vaxxed or not, are not getting Omicron no matter how many Omicron cases they are around.
And the people who *thought* they had covid because the test was a false positive really had the flu and had no antibodies to omicron.
Most likely any friend who thought they had covid based on a test result and later came down with covid probably never had it earlier.