I've got it again at the moment - this is the 3rd time (other half gave it to me, he tested positive day after returning from our recent cruise). Think I've had 3 of the main variants now, Original, Delta and now Omicron. Fully vaccinated, work in a primary school, first 2 were definately contracted from there, but can't blame them for the Omicron. Although there were 800+ kids on our cruise. I'm rhesus negative too, so that's had no bearing on my immunity. Only one in household who's not had it is my daughter, can't figure out why she's not had it yet, but she is able to self contain herself upstairs away from us, so may be that's the answer.