All are live vaccins except
**Core Concept**
Live vaccines contain a weakened or attenuated form of the pathogen, which replicates in the body and induces an immune response without causing the full-blown disease. This type of vaccine is used to confer long-term immunity and is particularly effective against viral infections. Examples of live vaccines include the MMR vaccine and the varicella vaccine.
**Why the Correct Answer is Right**
Live vaccines, by definition, contain a live but weakened or attenuated form of the pathogen, which allows them to replicate in the body without causing significant harm. This replication induces an immune response, leading to the production of antibodies and the activation of immune cells. In contrast, inactivated vaccines contain a killed or inactivated form of the pathogen, which does not replicate but still stimulates an immune response.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it is a live vaccine, which contains a weakened form of the pathogen that replicates in the body.
**Option B:** This option is incorrect as it is a live vaccine, which contains a weakened form of the pathogen that replicates in the body.
**Option D:** This option is incorrect as it is a live vaccine, which contains a weakened form of the pathogen that replicates in the body.
**Clinical Pearl / High-Yield Fact**
When administering live vaccines, it is essential to follow proper immunization protocols to avoid the risk of vaccine-strain disease in individuals with compromised immune systems.
**Correct Answer: C.**