If their standards are the same as last year, that counts. The admissions rep said that they basically anything can count as work experience, but they look more favorably on things related to public health (even tenuously) and positions held for longer than a few months/more than a few hours a week. You can contact them for a more thorough explanation. I'd be very explicit and ask "Does X, Y, and Z count as 2 years of work experience?" I didn't get the impression this was a very strict admissions criterion, but it's Harvard, so who knows.
[EDIT:] More up to date information on other threads proves me wrong! It's 2 years experience after undergrad.
