To study the prevalence, risk factors, and dynamics of pneumococcal carriage in infancy.Study design
In a population-based prospective cohort study conducted in Rotterdam, the Netherlands between June 2003 and November 2006, nasopharyngeal swabs were obtained from children at age of 1.5, 6, and 14 months. Data on risk factors were obtained from midwives, hospital registries, and questionnaires.Results
The prevalence of pneumococcal carriage increased from 8.3% at age 1.5 months (n = 627) to 31.3% at age 6 months (n = 832) and 44.5% at age 14 months (n = 757). The prevalence of serotypes covered by the 7-valent conjugate increased from 3.0% to 16.2% and 27.7% at these respective ages. Having siblings (adjusted odds ratio [aOR] = 4.33; 95% confidence interval [CI] = 1.22 to 15.35) and day care attendance (aOR = 3.05, 95% CI = 1.88 to 4.95 at 6 months; aOR = 2.78, 95% CI 1.= 70 to 4.55 at 14 months) were associated with pneumococcal carriage. Pneumococcal carriage at age 6 months was associated with pneumococcal carriage at age 14 months (aOR = 2.43; 95% CI = 1.50 to 3.94). Pneumococcal carriage was not associated with sex, maternal smoking, maternal educational level, or breast-feeding.Conclusions
The prevalence of serotypes covered by the 7-valent conjugate vaccine increased in the first year of life. Siblings, day care attendance, and previous pneumococcal carriage were independent factors associated with pneumococcal carriage.