I'd like to chime in here. I'm about to graduate with an MPH in Epidemiology and the field is a lot more flexible than you think. You are NOT just pigeonholed into research and government. You can absolutely do clinical things without having an RN or MD. Those positions may require additional certifications though. I worked as an Infection Control Practitioner for 2.5 years and may return to it eventually. It was a very nice practical application of Epidemiology. Yes, most positions are moving towards requiring an RN, but consider this.
An RN is going to need a crash course in stats and public health and outbreak investigation. An Epidemiologist will need a crash course in clinical standards of practice such as central line bandage changes, sterile processing and invasive device standards of practice. It isn't too hard! In fact, with just 2.5 years of experience I was approached for a Director position starting at 120k. MPH plus experience was acceptable to them. To be competitive you will need a Certification in Infection Control (CIC) especially if competing with RNs.
You can also do things like Industrial Hygiene. Industries you wouldn't even think of using an MPH, like ExxonMobil actually hire MPHs. Industrial hygiene involves things like occupational safety, OSHA requirements etc.
Additionally there are private sector companies, biotechnology for example, that use MPHs or Epis in Clinical Trial research!
Also if you are interested in laboratories, Biosafety is an emerging field. Less Epidemiology and more safety, but you could probably use your MPH to get into the field.
Edit: also, as far as stability goes, look at all the emerging and re-emerging diseases going on! Public health is about to explode. I bet there will be lots of jobs coming up. In Canada alone, 1500? 15,000? (Can't remember exact number) new positions will be created as result of new legislation that requires all labs using BSL-2 organisms to be licensed with the public health agency. Fancy heading up to our neighbors in the north?