I did an OAV treatment on an observation hive on August 26th. There was some brood present: both capped and uncapped. I did not see any brood die off. I have, however, seen them pull a limited number of drone pupae that had been uncapped when I did an OAV treatment. I think they were probably the drone brood that was directly over the vaporizer when I treated. Notice the white film over the eyes and antennae in the picture. From what I saw in the observation hive, the only react to the OAV when it contacts their eyes and antennae and does not seem to irritate any other part of the bee. Most pupae would be protected since they are capped. But, the eyes and antennae of an uncapped pupa would not be protected and they would be unable to clean themselves off and thus might suffer some damage if directly over the vaporizer where large amounts of oxalic acid could accumulate on them.