Background: The prevalence of pneumococcal carriage varies widely across communities. This variation is not fully explained by risk factors at the individual level but may be explained by factors producing effects at both the individual and community levels, such as child-care center (CCC) attendance.
Methods: We developed a transmission model to evaluate whether the combined risks of attending CCCs and associating with playmates who attend CCCs account for a large proportion of the variability in the prevalence of pneumococcal carriage across communities. We based parameters for the model on data from a multicommunity study.
Results: According to our model, differences in the proportion of children who attend CCCs can account for a range of 4%-56% in the prevalence of pneumococcal carriage across communities. Our model, which was based on data collected from 16 Massachusetts communities, predicts that the odds of carriage associated with CCC attendance are 2-3 times the odds associated with no CCC attendance (individual-level effect). The model also predicts that the odds of carriage for nonattendees in a community with CCCs are up to 6 times the odds for children in a community without CCCs (community-level effect). In addition, the mean number of hours spent at CCCs by a single attendee appears to exert effects on pneumococcal carriage that are independent of either the proportion of CCC attendance in the community or the mean number of hours these attendees spend in child care.
Conclusions: We used data from multiple communities to develop a transmission model that explains marked differences in pneumococcal carriage across communities by variations in CCC attendance. This model only accounts for CCC attendance among young children and does not include other known risk factors for pneumococcal carriage.