The Haemophilus influenzae vaccine contains which of the following
**Core Concept**
The Haemophilus influenzae type b (Hib) vaccine is designed to protect against invasive infections caused by Haemophilus influenzae type b, a bacterium that can lead to severe illnesses such as meningitis and sepsis. The vaccine is crucial in preventing Hib disease, particularly in children under the age of 5.
**Why the Correct Answer is Right**
The Hib vaccine contains **polysaccharide capsules** of the Haemophilus influenzae type b bacterium. These capsules, also known as **polyribosylribitol phosphate (PRP)**, are the primary virulence factor of the bacterium, allowing it to evade the host immune system. The vaccine induces an immune response against these capsules, providing protection against Hib infections.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the Hib vaccine does not contain **tetanus toxoid**, which is a component of certain combination vaccines such as DTaP (diphtheria, tetanus, and pertussis) but not Hib.
* **Option B:** This option is incorrect because the Hib vaccine does not contain **meningococcal polysaccharide**, which is a component of some meningococcal conjugate vaccines but not Hib.
* **Option C:** This option is incorrect because the Hib vaccine does not contain **pneumococcal polysaccharide**, which is a component of certain pneumococcal conjugate vaccines but not Hib.
**Clinical Pearl / High-Yield Fact**
The Hib vaccine is highly effective in preventing invasive Hib disease, with a vaccine efficacy of >90% in preventing meningitis and >95% in preventing sepsis. It is crucial to administer the Hib vaccine to all children under the age of 5 to prevent this potentially life-threatening disease.
**Correct Answer:** C. **polysaccharide capsules**