Characteristics of the children, nasopharyngeal bacterial colonization and viral detection rates.

Abbreviations: SD, standard deviation; NA, not applicable; PCV-7, 7-valent pneumococcal conjugate vaccine; URTI, upper respiratory tract infection.aDefined as more than 4 hours per week with at least one child from another family (yes/no).bDefined as use of an antibiotic, orally or intravenously administered with start date within 2 months before sampling date (yes/no). Of those, the prescribed antibiotic was amoxicillin (n = 69), penicillin (n = 1), amoxicillin/clavulanic acid (n = 3), a macrolide (n = 14; claritromycin (n = 8), azitromycin (n = 5), erythromycin (n = 1), a cephalosporin (n = 1, unknown type), and 3 unknowns.cParent-reported presence of mild symptoms of an upper respiratory tract infection (eg, a runny nose) at the time of sampling (yes/no).dPresence of enteroviruses and human parechovirus was determined in a subgroup of samples (N = 831) due to insufficient amounts of remaining nasopharyngeal swab material or nucleic acids to run these tests. Missing values were imputed by the single imputation procedure in multivariate analysis models in which these viruses were included to retain statistical power.