Here I have an anecdotal report from my own family.
The situation suggests that Omicron may be highly infectious even for those with recent prior infection with Delta. And obviously Omicron is sweeping through the vaccinated population as well*. Which might be a feature and not a bug for most of us, wether vaccinated or with natural immunity, both of which are really resistance to COVID, not immunity.
My brother recently attended a dinner party, at which 11 people were in attendance, one of whom was symptomatic (the next day) and tested positive for COVID that day, using a rapid antigen test as noted.
My brother and his companion (total 7 of 11) were infected with something, presumed COVID given the aforementioned positive test in the 21-year-old male attendee plus several other positive tests in some of the symptomatic attendees. But also one (1) negative test in a symptomatic individual. Symptoms were concerning but relatively mild for my brother, and quite serious for his previously-infected and double-vaxxed companion, still recovering. The 4 attendees not infected were unvaccinated, but one showed a positive test a year prior for COVID antibodies (natural immunity).
And yet my brother very recently had COVID (symptom onset ~Nov 22 2021). His companion’s prior COVID infection goes back some months, a much longer gap between prior infection plus she was double-vaxxed on top of infection. But for my brother, it has been only about 5 weeks after getting over it (presumably Delta).
I’m a big fan of natural immunity and COVID has not touched me since April 2020 in spite of an infected wife and daughter, from whom I did not isolate (!). But if this is indeed COVID at work, then the mutated Omicron virus is showing a very impressive ability to reinfect.
Is it possible that the infection was something else, such as influenza or RSV? Maybe, but multiple positive tests in multiple people suggest otherwise. Also, my brother states that the feel of the infection was the same as with his late November ordeal, just much less bad.
I wonder if Vitamin D is involved? Because he lives moderately far north, and has had zero sun exposure in any clinical sense.
The bright side
Suppose that Omicron is going to infect all vaccinated people and all those with natural immunity. Then I reiterate my “gift to the world” suggestion about Omicron. Because COVID is here to stay forever (endemic), apparently and we are all going to get it. So we might as all deal with it as a population with a relatively mild variant, gaining natural immunity for nearly everyone. Which like vaccinations, will give us all resistance to reinfection, not unqualified immunity.