Earlier quoted context omitted.
> what would it even mean for somebody to be "90% immune" to a disease? Hasn't this virus already mutated to a bunch of different strands? Could it mean you're immune to 90% of the known variations of the virus?
The variations are enough to have differences in infectiousness and to allow us to trace the spread a bit, but as far as we know immunity to any of them is immunity to all of them.
Because the reports from Denmarks Mink fiasco indicated that antibodies were not as effective on the mutation that appeared there short time ago. This would contradict the one-fits-all immunity argument.