## Core Concept
Measles elimination is a term used in public health to describe a stage in the control of measles where there is no continuous transmission of measles virus in a defined geographic area, even if importation of cases occurs. This concept is crucial for understanding the goals of measles control programs globally.

## Why the Correct Answer is Right
The correct answer, **C. Reduction in incidence to < 1 per 100,000 population per year**, aligns with the World Health Organization's (WHO) definition of measles elimination. This definition emphasizes that in an eliminated area, there should be less than 1 case per 100,000 population per year. Achieving this goal requires high vaccination coverage, robust surveillance to detect and respond to outbreaks quickly, and effective case management. ## Why Each Wrong Option is Incorrect - **Option A: Zero measles cases** - This option is incorrect because even in an eliminated area, importation of measles cases can still occur. Therefore, achieving zero measles cases is not a feasible or required criterion for elimination; rather, it's about maintaining a very low incidence. - **Option B: 90% reduction in measles cases** - This option is incorrect because a 90% reduction does not ensure that measles transmission has stopped. It only indicates a significant decrease in cases, which might not be sufficient to prevent outbreaks. - **Option D: 95% vaccination coverage** - While **95% vaccination coverage** is a critical strategy for achieving measles elimination, it is not the definition of elimination itself. Vaccination coverage is a tool to reach the goal, not the goal. ## Clinical Pearl / High-Yield Fact A key point to remember is that **measles elimination does not mean eradication**. Eradication implies that the disease has been completely removed from the globe, which requires interrupting transmission everywhere. Elimination is a more achievable and realistic goal for specific regions. ## Correct Answer: C. Reduction in incidence to < 1 per 100,000 population per year