**Core Concept**
Pneumococcal vaccines are designed to protect against Streptococcus pneumoniae infections, which can cause severe illnesses such as pneumonia, meningitis, and sepsis. The vaccines work by inducing immunity against the capsular polysaccharides of the bacteria, which are crucial for their virulence and survival.

**Why the Correct Answer is Right**
The pneumococcal vaccine is indeed derived from the capsular polysaccharides of Streptococcus pneumoniae. This polysaccharide-based vaccine stimulates the immune system to produce antibodies that can recognize and bind to the capsular polysaccharides, thereby preventing the bacteria from causing disease. The vaccine is available in both conjugate and polysaccharide forms, with the conjugate vaccine being more effective in young children.

**Why Each Wrong Option is Incorrect**
* **Option A:** Not given if age is less than 2 years - This is incorrect because pneumococcal conjugate vaccine is recommended for all children starting from 2 months of age, with a booster dose given at 12-15 months and a catch-up dose for children aged 24-59 months.
* **Option B:** Not given in splenectomy patients - This is incorrect because pneumococcal vaccination is actually recommended for patients who have undergone splenectomy, as they are at increased risk of invasive pneumococcal disease.
* **Option D:** Derived from capsular protein - This is incorrect because pneumococcal vaccines are derived from the capsular polysaccharides, not proteins.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that pneumococcal conjugate vaccine is more effective in young children, and a booster dose is required to maintain immunity. Additionally, individuals with certain medical conditions, such as splenectomy, are at increased risk of pneumococcal disease and should receive vaccination.

**Correct Answer:** C. Polyvalent