**Core Concept**
The duration of validity of yellow fever vaccination is a critical aspect of travel medicine, especially for individuals traveling to regions with a risk of yellow fever transmission. The World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) provide guidelines on the validity of yellow fever vaccination.

**Why the Correct Answer is Right**
The yellow fever vaccine is a live, attenuated vaccine that provides long-term immunity. According to the WHO and CDC, a single dose of yellow fever vaccine is valid for 10 years. This duration of immunity is based on the vaccine's ability to stimulate a strong and persistent immune response, which provides protection against yellow fever virus. The vaccine's efficacy is maintained through the production of antibodies against the virus, which are detectable for an extended period.

**Why Each Wrong Option is Incorrect**
**Option A:** This option suggests a shorter duration of validity than the actual 10 years. This is incorrect because the yellow fever vaccine provides long-term immunity, and a shorter duration would not be supported by scientific evidence.

**Option B:** This option suggests a longer duration of validity than the actual 10 years. Although some studies have suggested that the yellow fever vaccine may provide immunity for life, the WHO and CDC recommend a 10-year validity period to ensure consistent and standardized protection.

**Option C:** This option suggests that the duration of validity depends on individual factors, such as age or health status. While individual factors may influence the immune response, the WHO and CDC recommend a standardized 10-year validity period for the yellow fever vaccine.

**Option D:** This option suggests that the yellow fever vaccine requires booster doses to maintain immunity. However, the WHO and CDC recommend a single dose, and booster doses are not required to maintain protection against yellow fever virus.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the yellow fever vaccine is not a substitute for other recommended travel vaccinations and medications. Travelers to regions with a risk of yellow fever transmission should consult with a healthcare professional to determine the necessary vaccinations and precautions.

**Correct Answer:** C. 10 years.