**Core Concept**
Yellow Fever vaccination is a live, attenuated vaccine that provides immunity against yellow fever virus. The vaccine contains a weakened form of the virus, which triggers an immune response in the body, leading to the production of antibodies that neutralize the virus.

**Why the Correct Answer is Right**
The yellow fever vaccine is known to start providing protection against yellow fever virus 10 days after injection. This is because the attenuated virus in the vaccine takes around 10 days to replicate and stimulate an immune response in the body, leading to the production of antibodies that neutralize the virus. The immune response is thought to be mediated by the activation of CD4+ and CD8+ T cells, as well as the production of antibodies by B cells.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the yellow fever vaccine takes longer than 5 days to start providing protection.
**Option B:** This option is incorrect because the yellow fever vaccine does not start providing protection immediately after injection.
**Option C:** This option is incorrect because the yellow fever vaccine takes longer than 15 days to start providing protection.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the yellow fever vaccine is a live, attenuated vaccine, and therefore, it should not be administered to individuals with weakened immune systems, such as those with HIV/AIDS or taking immunosuppressive medications.

**Correct Answer: C. 15 days.**