The potential indirect effect of conjugate pneumococcal vaccines.

Pneumococcal conjugate vaccines are highly effective in preventing invasive disease in infants and young children, with favorable safety and immunogenicity profiles. These pediatric vaccines have also shown efficacy in reducing cases of non-invasive disease (i.e. otitis media, pneumonia). Recently, pneumococcal conjugate vaccines have demonstrated additional protective qualities that may enhance their use worldwide. For example, they can reduce nasopharyngeal acquisition of vaccine-specific serotypes of Streptococcus pneumoniae, which may in turn reduce the incidence of pneumococcal disease among non-vaccinated individuals; this is termed indirect or herd immunity. Although the emergence of antibiotic-resistant strains has complicated disease management, pneumococcal conjugate vaccines have been shown to protect against pneumococcal disease caused by such strains because most antibiotic-resistant strains are of the serotypes included in these vaccines. Thus, widespread use of these conjugate vaccines may prevent disease by providing both direct and indirect immunity, and may reduce the use of antibiotics and the development of antibiotic resistance worldwide.