Prelim Interviews at Hospitals Affiliated with Same School

When we interview for a prelim program with multiple affiliated hospitals, do we need to interview at each hospital separately? For example, if we choose all Harvard prelims (MGH, BWH, BID, Mt. Auburn), do we have to interview at each place separately, or is it just a single interview? Trying to minimize prelim interviews as I have a derm away in November. Thanks!
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums