You are definitely an ideal candidate for any MPH program! Granted a GRE score >50% in each section is ideal, however, MPH programs are looking for EXPERIENCE. MPH programs weigh your GRE score more heavily when you are lacking in experience or have a low GPA. Bottomline, they look at the application as a whole (i.e., personal statement, GRE, personal statement, experience and LOR's)
As for Yale, you're in. However, make sure it's the ideal program for you don;t just look at the name. In terms of public health programs, yale is certainly not the top school (of course it all depends on what you want to concentrate in). Unsure about harvard, although I do know that they won't even look at your application if you don't have significant experience or a professional degree. Goodluck!