Last I checked, you need Yellow Fever and Cholera. You may need to be up-to-date on Tetanus, measles, etc. You should already be vaccinated against polio. Many travellers get a gamma-globulin or immunoglobulin shot for an immune booster. The hepatitis vaccines have been introduced since I was last there – they are probably required now (they are required for neighboring Cameroon). You should also secure a supply of anti-malarials before you travel, and be aware that many of them require you to start taking them before you leave.