Preterm Children Have Higher Risk Than Full-term Children of Invasive Pneumococcal Disease During the First 2 Years of Life.

BACKGROUND: A few previous studies have reported an increased risk of invasive pneumococcal disease (IPD) in children born preterm, but this has not been investigated in a cohort study. The impact of 7-valent pneumococcal conjugate vaccine (PCV7) on IPD incidence rates in preterm children is unknown.

METHODS: Data from the Medical Birth Registry of Norway (2002-2010) were linked to other national registries. In total, 628,138 children were included in our study and followed until 2 years of age. Incidence rate ratios (IRRs) and confidence intervals (CIs) were estimated with Poisson regression.

RESULTS: We identified 411 cases of IPD. We observed higher rates of IPD in preterm than in full-term children for the intervals 0-23, 0-5 and 6-23 months of age, IRRs = 1.83 (95 % CI: 1.36-2.47), 2.95 (95% CI: 1.44-6.06) and 1.69 (95% CI: 1.22-2.34), respectively. The risk for IPD was reduced in the PCV7-period (2007-2010) compared with that of the pre PCV7-period (2002-2005) for children 6-23 months of age, IRRs = 0.20 (95% CI: 0.08-0.53) for preterm children and 0.28 (95% CI: 0.21-0.38) for full-term children, but not for those 0-5 months of age, IRRs = 1.94 (95% CI: 0.48-7.80) and 0.71 (95% CI: 0.38-1.33).

CONCLUSIONS: Preterm children had an increased risk of IPD. After introduction of PCV7, the rate of IPD was reduced among preterm and full-term children from 6 months of age.