The Center for Disease Control provides tips on preparing to travel, safety while in country, staying healthy, travel warnings, immunizations for every age of person traveling, things to take with you, and other travel related tips and resources. I would suggest thoroughly checking out this site before you leave.
The immunizations they recommend are: Yellow Fever, Hep A and Hep B, Rabies, Typhoid, Meningitis and Polio along with regular updates for all immunizations. Malaria is only needed outside of Addis Ababa.
We got all of these and so did our two elementary aged daughters who traveled with us. We believe in immunizations. We have lived in a third world country and seeing what preventable diseases can do to a person, a community and a nation......... well, we believe in immunizations.
Staying Healthy in Country
I would recommend that you take for at least a week before going some sort of pro-biotic like Acidophiles tablets. They come in all sorts. A great form is the non refrigerated Pearl. You can get it at Walmart. We like the chewable ones at Kroger related stores for kids.You should continue to take this while you are there and after you come home for a time. Hey, why not just keep taking it, it's good for you anyway. :)
I would also suggest taking an immune booster like Airbornebefore you travel and while you are there. Take it every day. You will be exposed to many different virus' and you DON'T want to catch them.
If you have environmental allergies or asthma. The smog is horrendous. You will NEED your meds, any you can possibly take. Also take decongestant and a cough syrup like Delsym. Just take your antihistamine every single day.
Other medications I would suggest are: Scabies cream Permethrin 5%, Ring worm treatment Lotramin Ultra, Pure Tea Tree Oil for this also. Children's medications for cold and allergies. Pain meds and IcyHot for the new muscles you will develop carrying around your new child.
If you can manage this, I would suggest taking a water purifierwith you. REI sells a ultraviolet light SteriPen which is awesome. You just stick it in the jug for a certain amount of time and wa-la you have pure water. We used that and it was great. Or you can buy water. Drink LOTS of water.
For altitude: We have always lived over 6000 feet, so the altitude did not bother us. But, for many of our guests we have learned some great tips. In order to thin your blood and thereforeneed less oxygen you should take an Aspirin each day (like Bayer's not Advil). In order to help your blood absorb more oxygen you should take several Tums or Rolaids each day. Avoid as much caffeine as possible (yeah right, tired parents need their caffeine, plus the great Ethiopian coffee), well balance it with more water than you would ordinarily drink, hence that SteriPen. You will feel better and function better and not be as tired.