**Core Concept**
Vaccine Vial Monitors (VVMs) are temperature-sensitive devices used to assess the integrity of the cold chain in vaccine storage and transportation. They change color in response to temperature fluctuations, indicating whether vaccines have been exposed to temperatures outside the recommended range.

**Why the Correct Answer is Right**
VVMs are designed to indicate whether vaccines have been exposed to temperatures outside the recommended range. The colors on the VVM change in response to temperature fluctuations, with the goal of indicating whether the vaccine has been compromised. If the VVM has changed color, indicating that the vaccine has been exposed to temperatures outside the recommended range, it is an indication that the vaccine is no longer effective and should be discarded.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not specified, but generally, VVMs change color at specific temperature thresholds (e.g., 25°C, 37°C). If the VVM has not changed color, it does not necessarily mean the vaccine is safe.
* **Option B:** This option is not specified, but VVMs are not designed to detect specific pathogens or contaminants. Their primary function is to indicate temperature-related degradation.
* **Option C:** This option is not specified, but VVMs are not designed to detect changes in vaccine potency or effectiveness directly. However, if a VVM has not changed color, it is an indication that the vaccine has not been exposed to temperatures outside the recommended range.

**Clinical Pearl / High-Yield Fact**
VVMs are an essential tool for maintaining the integrity of the cold chain, ensuring that vaccines remain effective and safe for administration. It is essential to monitor VVMs regularly and discard vaccines if they have been exposed to temperatures outside the recommended range.

**Correct Answer:** C.