Which of the following best describes the hallmark of a conjugated vaccine?

• A. It is composed solely of killed bacterial cells.
• B. It uses inactivated toxins to stimulate immunity.
• C. It links a polysaccharide antigen to a protein carrier to enhance immunogenicity.
• D. It contains only live attenuated microorganisms.

Answer: (C)

Verified step by step guidance

1. Understand that conjugated vaccines are designed to improve the immune response to certain types of antigens, particularly polysaccharides, which alone often produce a weak immune response, especially in young children.
2. Recognize that polysaccharide antigens are components of bacterial capsules that can be poorly immunogenic because they do not effectively stimulate T-cell dependent immunity.
3. Learn that conjugated vaccines work by chemically linking (conjugating) the polysaccharide antigen to a protein carrier, which helps recruit T-cell help and enhances the overall immune response.
4. Compare this mechanism to other vaccine types: killed bacterial cells (whole-cell vaccines), inactivated toxins (toxoids), and live attenuated microorganisms, noting that these do not involve linking polysaccharides to proteins.
5. Conclude that the hallmark of a conjugated vaccine is the linkage of a polysaccharide antigen to a protein carrier to enhance immunogenicity, making it distinct from other vaccine types.