While it’s reasonable to assume there would be notable sever case if the virus is ‘out there’.
You know what they say about assuming.
After all, we know it’s very transmittable (latest estimate I’ve seen: R0 =2.2).
it’s reasonable to look for those immunized.
It doesn’t cost much or take away from other efforts.
I have no objection to the great Unicorn hunt.
I just find it an amusing variation on the denial theme.