Which type of vaccines are polysaccharide vaccines?

Polysaccharide vaccines are designed to target specific polysaccharide components of bacterial capsules. These vaccines function by using pure polysaccharides from the outer capsule of bacteria to stimulate an immune response, particularly in the form of antibody production.

Pneumococcal and meningococcal vaccines are excellent examples of polysaccharide vaccines because they are formulated using polysaccharide antigens derived from the surfaces of the Streptococcus pneumoniae and Neisseria meningitidis bacteria, respectively. The polysaccharide nature allows these vaccines to elicit a T-cell independent immune response, typically resulting in a lower immunogenic response in young children compared to polysaccharide-protein conjugate vaccines.

This specificity to polysaccharide antigens distinguishes them from the other types of vaccines listed. Live vaccines involve weakened forms of pathogens, inactivated vaccines utilize killed pathogens, and diphtheria and tetanus vaccines are primarily toxoid vaccines, which are different categories that do not fit the definition of polysaccharide vaccines. Hence, the selection of pneumococcal and meningococcal vaccines as polysaccharide vaccines is accurate and reflects their underlying immunological principles.