**Core Concept**
Yellow fever vaccination is a crucial aspect of international travel, particularly to endemic areas in Africa and South America. The World Health Organization (WHO) has established guidelines for the certification of yellow fever vaccination, which includes the validity period of the certificate.

**Why the Correct Answer is Right**
The yellow fever vaccine is a live, attenuated vaccine that provides long-term immunity. According to the WHO, a valid yellow fever vaccination certificate is considered to be a proof of vaccination for a period of 10 years from the date of vaccination. This means that a person who has been vaccinated against yellow fever does not need to be revaccinated for 10 years as long as they have a valid certificate.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the validity period of the yellow fever vaccination certificate is not 5 years. The 10-year validity period is a widely accepted standard.
**Option B:** This option is incorrect because the yellow fever vaccine is a live, attenuated vaccine, and the validity period of the certificate is not based on the type of vaccine used.
**Option C:** This option is incorrect because the validity period of the yellow fever vaccination certificate is not 15 years. The 10-year validity period is a widely accepted standard.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the yellow fever vaccination certificate must be issued by an authorized vaccination center and must include the date of vaccination, the name and address of the vaccinator, and a serial number. Travelers to endemic areas should ensure that their vaccination certificate is valid for at least 10 years from the date of vaccination.

**Correct Answer: D. 10 years.**