**Core Concept**
The mumps vaccine is a live, attenuated virus vaccine used to prevent mumps infection. It is part of the MMR (measles, mumps, and rubella) vaccine and is derived from a specific strain of the mumps virus.

**Why the Correct Answer is Right**
The **Jeryl Lynn** strain is the most widely used and standardized live attenuated mumps vaccine strain. It was developed in the 1960s and is the basis of the MMR vaccine used globally. This strain is known for its high efficacy and safety profile in preventing mumps.

**Why Each Wrong Option is Incorrect**
Option B: **Edmonshon Zagreb** is a strain used in some regional vaccines, particularly in Eastern Europe, but it is not the standard global mumps vaccine.
Option C: **Schwatz** is a strain used in some early mumps vaccines, but it is not the current standard and is less commonly used.
Option D: **Moraten** is a name associated with a different vaccine (e.g., for other diseases) and is not related to mumps.

**Clinical Pearl / High-Yield Fact**
The Jeryl Lynn strain is the only strain used in the current MMR vaccine worldwide. Always remember that "Jeryl Lynn" is the key name to recall for mumps vaccine in exams.

✓ Correct Answer: A. Jeryl Lynn