The Pneumococcal vaccine protects against which organism and related diseases?

• A. Neisseria meningitidis
• B. Streptococcus pneumoniae causing pneumonia, meningitis, endocarditis
• C. Haemophilus influenzae type B
• D. Staphylococcus aureus

Answer: (B)

The main idea is recognizing which pathogen the pneumococcal vaccine protects against and the diseases it helps prevent. The pneumococcal vaccine targets Streptococcus pneumoniae, a bacterium that can cause a range of invasive and noninvasive diseases. It is a major cause of pneumonia and meningitis, and it can also lead to bacteremia and other serious infections such as endocarditis. Vaccination reduces the risk of these pneumococcal diseases across multiple serotypes covered by the vaccine.

The other organisms listed are different pathogens with their own vaccines or disease profiles (for example, Neisseria meningitidis with meningococcal vaccines, Haemophilus influenzae type B with Hib vaccine, and Staphylococcus aureus for which there isn’t a widely used vaccine). That’s why the correct match is Streptococcus pneumoniae and its associated illnesses like pneumonia and meningitis, and the inclusion of endocarditis reflects invasive pneumococcal disease in general.