Focus on pneumococcal vaccines and nasopharyngeal carriage

Abstract

Abstract The vaccination is the only available tool to prevent disease caused by Streptococcus pneumoniae. In this review emphasis was given on pneumococcal conjugate vaccine (PCV) and S. pneumoniae nasopharyngeal carriage, as nasopharynx colonization precede invasive disease. To optimize the development of future conjugate vaccines and to evaluate their efficacy, it is necessary to understand the serogroup specific epidemiology of pneumococci and their associated disease types. Continuous monitoring of S. pneumoniae serotypes is essential since it has been shown that the incidence of types responsible for invasive disease can change over time. The extended protection increases the cost effectiveness of PCV and should clearly encourage its use in poorly resourced countries. However, the accumulated experience also shows that the herd immunity, due to PCV, is partly offset by replacement of the vaccine serotypes by other, nonvaccine serotypes. Owing to the general reduced virulence of the latter, this has only had a modest effect on disease, but the possibility of more virulent nonvaccine serotypes arising cannot be ignored and should be the focus of continued surveillance.