Pneumococcal Vaccine

Kim, Sung Han; Woo, Jun Hee

Abstract

Streptococcus pneumoniae causes considerable morbidity and mortality. There are currently two types of pneumococcal vaccine available under license: pneumococcal polysaccharide vaccines(PPV23) and pneumococcal conjugate vaccines(PCV-7). PPV23 contains T-cell independent antigens which stimulate mature B lymphocytes and produce an effective antibody response. However T-lymphocytes are not involved which leads to an absence of immunological memory and lack of an anamnestic response on challenge. The 23-valent vaccine is reported to be effective in older children and adults, and is currently recommended for high-risk patients such as hyposplenic patients and the general elderly population. PPV23 appears cost effective for elderly patients PCV-7 has high efficacy against radiological pneumonia and invasive pneumococcal disease, acute otitis media, reduces the nasopharyngeal colonization rate of vaccine strain, and provides herd immunity. PCV-7 may also provide an effective new tool to reduce disease caused by drug-resistant strains of pneumococci. But this vaccine has limited serotype coverage, replacement phenomena. It remains unknown if long-term serotype shifts would be caused by PCV-7. And the possibility of the spread and acquisition of virulent non-vaccine serotypes is a real threat which must be monitored. New PCVs including more serotypes could prove to be good options in the future for all age groups. Several protein-based pneumococcal vaccine candidates (currently under investigation in animal models) offer the potential advantage of serotype independent protection in the near future.