This is probably still an improvement, though. I haven't seen it happen often, but I've certainly seen cases of BCG instillation backtrack into the central circ

This is probably still an improvement, though. I haven't seen it happen often, but I've certainly seen cases of BCG instillation backtrack into the central circulation (my first case of this actually seeded his bone marrow with it), and then you've got a case of TB. If there's less morbidity if that happens here, and I presume there is, that's still better.