Which of the following is a live attenuated vaccine?
**Core Concept**
A live attenuated vaccine is a type of vaccine that uses a weakened or attenuated form of a microorganism, such as a virus or bacteria, to induce an immune response without causing the full-blown disease. This approach allows for the stimulation of both humoral and cellular immunity, providing long-term protection against future infections.
**Why the Correct Answer is Right**
The correct answer is a live attenuated vaccine because it contains a weakened form of the virus, which is unable to cause disease but still stimulates an immune response. This is in contrast to inactivated vaccines, which use a killed form of the virus and may not provide the same level of immunity. The live attenuated vaccine is often given orally, such as in the case of the Sabin poliovirus vaccine, to provide mucosal immunity and prevent the spread of the virus.
**Why Each Wrong Option is Incorrect**
* **Option B:** This is incorrect because it is an inactivated vaccine, which uses a killed form of the virus to stimulate an immune response.
* **Option C:** This is incorrect because it is a subunit vaccine, which uses a specific component of the virus, such as a protein, to stimulate an immune response.
* **Option D:** This is incorrect because it is a conjugate vaccine, which combines a weakened form of the virus with a carrier protein to enhance the immune response.
**Clinical Pearl / High-Yield Fact**
Live attenuated vaccines can cause mild side effects, such as fever or rash, due to the presence of a weakened form of the virus. However, these vaccines are often more effective than inactivated vaccines and provide long-term protection against future infections.
**Correct Answer: C. MMR vaccine is a live attenuated vaccine.**