Streptococcus-Pneumoniae Diseases

Abstract

Streptococcus pneumoniae is a Gram-positive encapsulated diplococcus. The capsule determines the ≥100 serotypes, is the relevant vaccine antigen and the main pathogenicity factor. Children <5 years are the main reservoir and often spread S. pneumoniae to the elderly. Presence of an acute viral respiratory tract infection (ARI) may favor the development of mucosal pneumococcal infections, as theoretical, experimental, epidemiological, and clinical data indicate viral-bacterial synergy. Many risk factors like anatomical and immunological factors, underlying diseases, and environmental/behavioral factors favor development of invasive pneumococcal disease (IPD). Pneumococcal diseases can be treated with different groups of antibiotics, depending on the local resistance situation. Polysaccharide and polysaccharide-conjugate vaccines are used for pneumococcal disease prevention. The disadvantages of 23-valent pneumococcal polysaccharide vaccine (Pneumovax®) are: lack of memory cell induction, and thus no booster response, no reduction of carriage, and thus no herd protection, lack of IgG immune response in children <2 years, only short-term and moderate protection rates in subjects ≥65 years against bacteremic pneumonia only. In contrast, pneumococcal conjugate vaccines (PCVs): generate a memory response in all ages, can reduce pneumococcal acquisition/colonization, reduce mucosal diseases (otitis media, non-bacteremic pneumonia, IPD), and there is long-term protection. Currently licensed and marketed PCVs are PCV10 (Synflorix®, not licensed in the USA; indicated only for children), PCV13 (Prevenar 13® [Europe]; Prevnar 13® [USA]) and PCV15 (Vaxneuvance®) which are both licensed in EU and USA for adults and children, and PCV20 (Prevnar 20® [USA]; Apexxnar® [Europe]) which is currently only licensed for use in adults.