**2. Types of antipneumococal vaccines**

The pneumococcus is surrounded by a polysaccharide capsule, and differences in this capsule permit serological differentiation into distinct serotypes (Hausdorff 2005). However, the existence of more than 90 distinct serotypes (differing in their chemical composition, potential immunogenicity and epidemiological impact on different population groups) has greatly complicated the development and evaluation of anti-pneumococcal vaccines.

At the moment, there are 3 established approaches to anti-pneumococcal vaccination: capsular polysaccharide pneumococcal vaccines (PPV), protein-polysaccharide conjugate pneumococcal vaccines (PCV) and protein-based pneumococcal vaccines (PBPV) (Fedson 2003, Abraham Van-Parijs 2004, Tai 2006). At present, only the "old" PPV-23 for use in adults and two "new" PCVs (PCV-10 and PCV-13), both licensed in 2010 for use in children, are available in clinical practice.
