Pneumococcal vaccines – past, present and future

S. pneumoniae is a Gram-positive bacterium with a polysaccharide capsule, which is a virulence factor. More than 90 polysaccharide serotypes have been identified, with each serotype eliciting serotypespecific immune responses. Different serotypes vary in their propensity for nasopharyngeal colonisation and for causing disease. In Australia in 2002-04, before the universal infant pneumococcal conjugate vaccination program, 85% of invasive pneumococcal disease in children under two years was caused by the serotypes contained in the 7-valent conjugate vaccine (Table