Strengths and weaknesses of pneumococcal conjugate vaccines

Abstract

Multivalent vaccines addressing an increasing number of Streptococcus pneumoniae types (7-, 10-, 13-, 15-, 20-valent) have been licensed over the last 22 years. The use of polysaccharide-protein conjugate vaccines has been pivotal in reducing the incidence of invasive pneumococcal disease despite the emergence of non-vaccine serotypes. Notwithstanding its undoubtable success, some weaknesses have called for continuous improvement of pneumococcal vaccination. For instance, despite their inclusion in pneumococcal conjugate vaccines, there are challenges associated with some serotypes. In particular, Streptococcus pneumoniae type 3 remains a major cause of invasive pneumococcal disease in several countries.Here a deep revision of the strengths and weaknesses of the licensed pneumococcal conjugate vaccines and other vaccine candidates currently in clinical development is reported.

Keywords: Bacterial infection; Conjugate; Polysaccharide; Streptococcus pneumoniae; Vaccine.

Fig. 1

Schematic representation Streptococcus pneumoniae serotype 1 capsular polysaccharide repeating unit →4)-α-D-GalpA2/3Ac-(1→3)-α-D-GalpA-(1→3)-D-AAT-α-Galp-(1→.

Fig. 2

Schematic representation Streptococcus pneumoniae serotype 5 capsular polysaccharide repeating unit

Fig. 3

Schematic representation Streptococcus pneumoniae serotype 3 capsular polysaccharide repeating unit →3)-β-D-GlcpA-(1→4)-β-D-Glcp-(1→.

Fig. 4

Schematic representation of Streptococcus pneumoniae serotypes sharing similar structure for which cross-protection should be expected: (A) Spn-6A and Spn-6B; (B) Spn-19A and Spn-19F; (C) Spn-10A, Spn-10B, Spn-10C and Spn-10F.