Late March. It was a long wait... I was literally about to commit to another school in that same week.
That being said, the waitlist definitely moves!! It moves faster if those who got accepted but are not going declines asap; it moves slower if people take a long time to decide until the last minute.
Yes, I was interviewed twice in early January by two separate faculty members.
I'm not sure what's the number of interviews given out for this year. As for if people who get interviewed will be automatically accepted, speaking from my experience last year, I actually was waitlisted after being interviewed and was lucky enough to get off the waitlist. Hope this helps!
Harvard Population Health Sciences got a record number of applicants this year! With 800+ applicants but less than 40 spots across all PHS fields of study. Admission letters should be sent out any day now. Good luck everyone!