Which of the following statements correctly reflects a vaccine strategy against bacterial infections?

• A. PCV13 (pneumococcal) and Hib (Haemophilus influenzae type b) vaccines
• B. MMR and Varicella vaccines
• C. DTaP and Hepatitis B vaccines
• D. Influenza and Rotavirus vaccines

Answer: (A)

Vaccines against bacteria often focus on the bacterial capsule and use a conjugate design to produce a strong, lasting immune response in people of all ages, especially infants. The pneumococcal vaccine (PCV13) and the Hib vaccine target the capsule polysaccharides of two major bacteria that cause serious disease. By linking those polysaccharides to a protein carrier, they convert a weak, antibody response that usually happens to polysaccharides into a robust T-cell–dependent response with memory. This leads to better production of protective antibodies, reduces carriage in the throat, and lowers the risk of invasive infections like meningitis and pneumonia. That combination is a clear example of a strategy aimed at preventing bacterial infections. The other options largely involve vaccines against viruses (such as measles, mumps, rubella, varicella, influenza, rotavirus) or vaccines that neutralize bacterial toxins rather than targeting the bacteria themselves, so they don’t illustrate the same bacterial-capsule conjugate approach.