Usually, such feelings are not very harmful and do not lead to any lasting damage. If the feelings of shame are too high, the child simply usually will not agree to make sex. But sometimes such feelings may be too strong so that they can lead to damage.
The feelings of shame are independent of the participation of adults in the sexual activity. There seems to be no principle difference between such feelings relative to masturbation, to sex plays with age mates or to pedosexual relations.
If the adult has a positive relation to his sexuality, he can help to minimize such feelings.
Feelings of shame usually become much higher after the detection of the sexual activity.