Give you a link

Here is our university's link about O1 status.

http://www.hio.harvard.edu/students_scholars/visas_immigration/o_visa_status.php

O1的審理隻需幾天，拿到approval（I797)後需要到境外簽證回來才能生效（因為你沒有waiver,不能再境內轉換身份）。

Wish You Luck！