Are there deaf people work in hospital?

Of course! A deaf person has every right to work any where they wish to work.

Yes, in certain areas. It depends on what the person has to do. For example, it would be difficult for a deaf person to be a nurse. A nurse has to be able to communicate easily with a patient, and also has to be able to listen to the heart, lungs, bowels, etc. In many cases, the safety of the patient has to come first. If the person is unable to fulfill the duties of the job, then they don't get the job, whether they have an impairment of any kind or not.