Table 1.
Clinically important encapsulated bacteria and vaccines. PCV13, Pneumococcal polysaccharide conjugate vaccine 13; PPSV23, Pure pneumococcal polysaccharide vaccine 23. PRP-D, polyribosyl-ribitol-phosphate-Diphtheria toxoid (DT) conjugate vaccine; PRP-CRM, PRP-conjugate vaccine containing CRM197, a mutated DT protein; PRP-OMP, PRP conjugate vaccine containing meningococcal outer membrane protein; PRP-T, PRP conjugate vaccine containing tetanus toxoid. MPSV4, Tetravalent meningococcal polysaccharide vaccine; MCV4, tetravalent meningococcal polysaccharide conjugated with diphtheria toxoid or diphtheria CRM197 protein. Vaccines against N. meningitidis type B are directed to surface proteins rather than capsular polysaccharides. K antigens, surface exposed capsular polysaccharides in K. pneumoniae. Vi, Virulence antigen (shared capsular polysaccharides). A Vi-protein conjugate vaccine is in late-stage Phase 3 testing for efficacy, particularly in young children.
| Name (Gram Character and Morphology) | No. of Capsular Serotypes | Type of Illness | Annual Mortality (Cases) | Polysaccharide Vaccines Available | Refs |
|---|---|---|---|---|---|
| Streptococcus pneumoniae (Gram-positive cocci) | 94 | Pneumonia, Otitis media, Meningitis | 1.5 million (500,000 children ≤ 5 years of age) | PCV-13, PPSV-23 | [8,9] |
| Streptococcus agalactiae (Gram-positive cocci) | 9 (type 3 is predominant) | Neonatal sepsis, Meningitis, Pyrogenic infection | 150,000 neonates | None currently licensed | [10] |
| Haemophilus influenzae (Gram-negative coccobacilli) | 6 (a–f) (type b is predominant) | Pneumonia, Meningitis, Cellulitis, Arthritis | 371,000, especially children ≤ 4 years of age | PRP-D, PRP-CRM, PRP-OMP, PRP-T | [11,12] |
| Neisseria meningitidis (Gram-negative cocci) | 13 (5 types are predominant) | Meningitis, Pneumonia, Arthritis, Septicemia | 15,000 | MPSV4, MCV4 (types A, C, Y, and W-135) | [13,14] |
| Klebsiella pneumoniae (Gram-negative bacilli) | >78 K antigens (K2 and K1 are predominant) | Urinary tract infections, Pneumonia, Bacteremia | Not available | None currently licensed | [15,16,17,18] |
| Salmonella enterica serovar Typhi (Gram-negative bacilli) | 1 (Vi) | Enteric fever, Gastrointestinal infection, Septicemia | 150 to 210,000 | Ty21a (Oral live attenuated vaccine) and Vi PS* (injectable vaccine) | [1,19,20,21,22] |
| Bacteroides fragilis (Gram-negative bacilli) | 2 | Abdominal abscess | Not available | None currently licensed | [4,5,6] |