Answer:
Must occur within 12 months of the approval date.
Explanation:
Continuing review of a validated protocol should take place within 12 months of the endorsing date even in the absence or inability to pinpoint further risks.
Review by a convened IRB is not often necessary (take for instance, for a finished study plus data analysis only). Any unexpected problems must be dealt with in the course of the continuing review process, but the review has to entail certain information including the amount of subjects accumulated, any important latest literature, and a sample of the present consent form.