**Core Concept**
Freezing can denature proteins and disrupt the structural integrity of vaccines, rendering them ineffective or even harmful. Certain vaccines are sensitive to temperature fluctuations and require specific storage conditions to maintain their potency and safety.

**Why the Correct Answer is Right**
Vaccines containing live attenuated organisms, such as oral poliovirus vaccine (OPV) and rotavirus vaccine, should not be frozen. Freezing can cause the live organisms to become unstable, leading to a loss of potency or even reversion to a wild-type form, which can cause disease. This is because the freezing process can damage the viral coat and disrupt the balance of the viral replication cycle.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because some vaccines, such as MMR (measles, mumps, and rubella) and varicella, can be safely frozen and even stored at -20°C for long-term storage.
**Option B:** This option is incorrect because the correct answer has not been specified, but it is not relevant to the question.
**Option C:** This option is incorrect because the correct answer has not been specified, but it is not relevant to the question.

**Clinical Pearl / High-Yield Fact**
Live attenuated vaccines, such as OPV and rotavirus vaccine, require careful handling and storage to maintain their potency and safety. Always check the storage instructions for each vaccine to ensure proper handling and administration.

**Correct Answer:** D.