Here in Atlanta, Emory Hospital has a Travel Well Clinic that provides immunizations for people travelling out of the U.S. We made an appointment and had our evaluation.

We were asked about our travel, where we were going, when we were going, what areas of the country we would be traveling in (rural, metropolitan area, etc) and what kinds of accomodations we'd have. Our current immunization history was taken into account.

We were provided with a list of recommended immunizations with risk factors for each (the liklihood that we could contract a specific disease). We had to decide which ones we wanted. For China, travelling in the fall, it was recommended that we have the following immunizations:

Hepatitis A
Hepatitis B
Typhoid
Polio IPV
Dipthyria

We went with the recommendation and got our immunizations. In retrospect, however, I'm not sure it was necessary based upon our experience. We were always in big cities, staying in five star hotels, eating great food (mostly in the hotels) and took extra care not to drink the water. If this is a concern, consider where you will be travelling, weigh the risks and make your decision.