**Question:** Polysaccharide pneumococcal vaccine used in all EXCEPT

A. Inactivated polysaccharide pneumococcal vaccine (PPV23)
B. Conjugated pneumococcal vaccine (PCV13)
C. Haemophilus influenzae type b conjugate vaccine (Hib)
D. Measles, mumps, rubella (MMR) vaccine

**Correct Answer:** D. Measles, mumps, rubella (MMR) vaccine

**Core Concept:**
The polysaccharide pneumococcal vaccine is a type of vaccine that stimulates the immune system to recognize and respond to Streptococcus pneumoniae (pneumococcus), a bacterium that causes various infections, including pneumonia, meningitis, and bacteraemia. There are two main types of polysaccharide pneumococcal vaccines: Inactivated polysaccharide pneumococcal vaccine (PPV23) and Conjugated pneumococcal vaccine (PCV13).

**Why the Correct Answer is Right:**
The correct answer is D, the Measles, Mumps, Rubella (MMR) vaccine. This vaccine is primarily designed to protect against three viral infections caused by specific strains of the viruses:

1. Measles: A viral respiratory illness characterized by fever, rash, and respiratory symptoms.
2. Mumps: A viral infection causing fever, swelling of the salivary glands, and occasionally hearing loss or orchitis (inflammation of the testes).
3. Rubella: A viral infection causing high fever, rash, and joint pain.

**Why Each Wrong Option is Incorrect:**
A. Inactivated polysaccharide pneumococcal vaccine (PPV23) and Conjugated pneumococcal vaccine (PCV13) are designed to protect against pneumococcal infections caused by Streptococcus pneumoniae bacteria. They are distinct from the viral vaccines mentioned for MMR.

B. Conjugated pneumococcal vaccine (PCV13) is specifically designed to protect against 13 serotypes of Streptococcus pneumoniae bacteria. It is not related to viral infections like MMR vaccine.

C. Haemophilus influenzae type b conjugate vaccine (Hib) protects against Haemophilus influenzae type b, a different bacterial pathogen (Hib) causing serious infections like meningitis, pneumonia, and sepsis, which is not related to the viral infections covered by MMR vaccine.

D. The Measles, Mumps, Rubella (MMR) vaccine is a combination vaccine designed to protect against three viral infections caused by different viruses. It is unrelated to bacterial vaccines like PPV23 and PCV13, which are designed to protect against Streptococcus pneumoniae infections.

**Clinical Pearls:**

1. MMR vaccine is usually given before the PPV23 and PCV13 vaccines, as MMR can trigger a transient adverse reaction called "postvaccine fever syndrome", which can occur in 10-20% of recipients after MMR vaccination. This reaction is usually mild and self-