I'd presumed that most people would have been tested for immunity quite young and informed of their status by their parent(s)/guardian(s). On the assumption that this hypothesis is true, it's possible that Tuuri doesn't remember being told she was immune for whatever reason. How Onni's decision to lie about it came about and played out would be an interesting tale.
If there is a test and
unless there's some Hollywood science to make it undoable/unreliable until the patient has reached age X or somesuch (which would pretty much fly in the face of the hard either/or's we see in every other aspect of Rash and immunity), then we can assume that parents would want their children tested right after birth, if not sooner. Which is of course way too early for the child itself to remember it later on.
Second, we've seen people shuffle through paperwork of travelers, but there's no clear indication that a person's
immunity status is being mirrored into a document as thoroughly as a person's identity is with ID cards and passports in our day.
Which brings us to the fact that when Tuuri was 10 and Lalli 8, they and Onni
up and left Saimaa, leaving behind (presumably for dead)
all relatives, all the clerks issuing their documents, their neighbors, MDs,
everyone besides Onni and the hypothetical paperwork who could have told Tuuri about her immunity status if she did not already know full well at that point. (And even if she did, whatcha do when your older brother and head of the family tells you flat out that "you must be misremembering" ...)
Maybe his boots are just covered in ash and soot?
With all that ash and soot stopping
precisely at the fringe of the bootleg?
