Incidence of invasive Group B Streptococcal infection and the risk of infant death and cerebral palsy: a Norwegian Cohort Study

Group B Streptococcus (GBS) is the leading cause of invasive neonatal infection worldwide. In high-income countries mortality rates are 4–10%, and among survivors of GBS meningitis, 30–50% have neurodevelopmental impairments. We hypothesized that invasive GBS infection was associated with increased risk of infant mortality and cerebral palsy (CP). All children born alive in Norway during 1996–2012 were included. Data were collected from three national registers. Invasive GBS infection during infancy was categorized into early-onset disease (EOD), late-onset (LOD), and very late-onset disease (VLOD). Primary outcomes were infant mortality and CP. Invasive GBS infection was diagnosed in 625 children (incidence: 0.62 per 1000 live births; 95% confidence interval (CI): 0.57–0.67). The incidence of EOD was 0.41 (0.37–0.45), of LOD 0.20 (0.17–0.23), and of VLOD 0.012 (0.007–0.021). The annual incidence of LOD increased slightly. Among infected infants, 44 (7%) died (odds ratio (OR): 24.5; 95% CI: 18.0–33.3 compared with the background population). Among survivors, 24 (4.1%) children were later diagnosed with CP, compared with 1887 (0.19%) in the background population (OR: 22.9; 95% CI: 15.1–34.5). Despite a relatively low incidence of invasive GBS infection in Norway, the risk of death and CP remains high. Improvements in prevention strategies are needed.