Pneumococcal vaccine

A vaccine that protects against disease caused by Streptococcus pneumoniae by inducing immunity to bacterial serotypes or proteins. Available formulations include polysaccharide and protein-conjugate vaccines.

Capsular polysaccharide: A carbohydrate polymer forming the outer capsule of many bacteria. Pneumococcal vaccines target capsule sugars that distinguish serotypes.
Pneumococcal disease: Infections caused by Streptococcus pneumoniae, ranging from ear infections to pneumonia, meningitis, and bloodstream infection. Vaccination aims to prevent these illnesses and reduce their complications.
Streptococcus pneumoniae: A Gram-positive bacterium that commonly colonizes the upper respiratory tract and can cause serious disease. Its capsule and diverse serotypes shaped the design of pneumococcal vaccines.
Pneumococcal polysaccharide vaccine: A vaccine made from purified capsular polysaccharides from selected pneumococcal serotypes. Unlike conjugate vaccines, it does not reliably generate strong immune memory in young children.
Pneumococcal carriage: The presence of Streptococcus pneumoniae in the upper respiratory tract without symptoms of disease. Conjugate vaccination can reduce carriage of vaccine serotypes and interrupt transmission.
T-dependent antigen: An antigen that elicits an antibody response with help from antigen-specific T cells. Conjugate vaccines make pneumococcal sugars engage this pathway through their carrier proteins.
Pneumococcal pneumonia: Pneumonia caused by Streptococcus pneumoniae, a common bacterial cause of community-acquired pneumonia. Preventing this severe manifestation is a central goal of adult pneumococcal vaccination.
Pneumococcal serotype: A variant of Streptococcus pneumoniae defined principally by the structure of its capsular polysaccharide. The number and identity of included serotypes distinguish vaccine generations.
Pneumococcal conjugate vaccine: A vaccine that links pneumococcal capsular polysaccharides to carrier proteins. It differs from polysaccharide-only vaccines by recruiting T-cell help and reducing carriage.
Antimicrobial resistance: The ability of microbes to survive exposure to drugs that would normally inhibit or kill them. Preventing pneumococcal infections can reduce antibiotic use and the selective pressure it creates.

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