Two of the definitions for the word innocence are "simplicity; absence of guile or cunning; naiveté" and "lack of knowledge or understanding."
Based on those definitions, innocence could not have survived in anyone who survived the Holocaust. The sights, hardships, and struggles experienced by Elie and the others deported to the concentration camps would have destroyed any innocence that may have been present when the individuals first entered the camps.
Upon arriving at Buna, those who had been there longer told the newcomers about the camp. "Buna is a very good camp. One can hold one's own here. The most important thing is not to be assigned to the construction Kommando..." That kind of knowledge was essential to survival, even when it could not be directly used.
Elie became wise to the ways of the camp, to the things that had to be done in order in increase his chances of survival, as did everyone else in his position. Innocence would have been a serious handicap to the chances of survival for anyone in the concentration camps.