**Core Concept**
Yellow fever is a viral disease caused by the yellow fever virus, transmitted by the bite of an infected Aedes mosquito. Vaccination is the most effective method of preventing yellow fever.

**Why the Correct Answer is Right**
The yellow fever vaccine is a live attenuated vaccine that contains a weakened form of the yellow fever virus. This vaccine stimulates the body's immune system to produce antibodies and activate immune cells, such as T-cells, to fight the virus. The vaccine is administered subcutaneously and provides long-term immunity against yellow fever. The World Health Organization (WHO) recommends the yellow fever vaccine for travelers to endemic areas, and it is also required for entry into certain countries.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the yellow fever vaccine is not a killed-virus vaccine, but rather a live attenuated vaccine.

**Option B:** This option is incorrect because there is no vaccine specifically designed to prevent yellow fever in animals, although there are measures to control the spread of the disease in animal populations.

**Option C:** This option is incorrect because the yellow fever vaccine is not a conjugate vaccine, which is a type of vaccine that combines a weakened form of a pathogen with a carrier protein to enhance immune response.

**Clinical Pearl / High-Yield Fact**
The yellow fever vaccine is a contraindication for individuals with certain immunodeficiency disorders, such as HIV/AIDS, and for those who have received immunosuppressive therapy.

**Correct Answer:** D. 17D live attenuated vaccine