It depends on the school. Usually, if you are not accepted off the waitlist then you are technically a re-applicant to most schools. Therefore you have to do another secondary and you should have had some "improvement" from the previous year.
I know that Touro-NV, if you are waitlisted and not accepted that you are automatically reviewed again for the next school year without doing another secondary ect. They even said that they interview those people before the first official interview date for the normal cycle.
So in short, it depends on the school.