Prevalence and risk factors of nasopharyngeal carriage of Streptococcus pneumoniae in healthy children in Japan.

The findings of this study revealed a 22% prevalence of Streptococcus pneumoniae among healthy children in Japan; the prevalence tended to increase with age. We identified attendance at day-care facilities and the presence of older siblings as the major risk factors associated with pneumococcal carriage. A significant decrease in pneumococcal colonization was observed among children during the summer; however, a seasonal variation was independent of various factors. Our findings suggest that prior immunization with heptavalent pneumococcal conjugate vaccine within the current recommended schedule is required for children exposed to these risk factors.