The Peloran Treatments did have a side effect.  It was one that no testing in any reasonable number could have found.  It happened one in a million times.  That’s one ten thousandth of a percent.  It’s not even a blip.  That girl in New Orleans, Clarice Beaumont, was our first clue.  First she aged seven years in the span of two, and then she stopped altogether.  It’s been almost two centuries now, and she hasn’t Aged another day.