I used the same beginning essentially for each one, and then tweaked phrases here and there to reflect the specific department. When I spoke about why I wanted to go to XYZ/why I'm a perfect fit there, that is when I made it completely different and highlighted the things I liked about the specific program.
I looked at 10 different SOP prompts and this is how I summarized the guidelines (the bolded ones are what changed for me with each essay to each school):
1. Reason for interest in public health (why?)
2. Formative experiences in public health (area of interest/public health issue should be clear)
3. Why a particular department/concentration (introduce research interests)
4. Why the university/program - how would you be a good fit
5. How you will use your degree to achieve career goals/what skills or experiences do you hope to gain as you complete your MPH coursework at XYZ, that will help propel your career in public health?