Early-onset group B streptococcal infections in five Nordic countries with different prevention policies, 1995 to 2019

Background: Neonatal early -onset disease caused by group B Streptococcus (GBS) is a leading cause of infant morbidity. Intrapartum antibiotic prophylaxis (IAP) is effective in preventing early -onset GBS disease, but there is no agreement on the optimal strategy for identifying the pregnant women requiring this treatment, and both risk -based prophylaxis (RBP) and GBS screening -based prophylaxis (SBP) are used. Aim; The aim of this study was to evaluate the effect of SBP as a public health intervention on the epidemiology of early -onset GBS infections. Methods: In 2012, Finland started the universal SBP, while Denmark, Iceland, Norway and Sweden continued with RBP. We conducted an interrupted time series analysis taking 2012 as the intervention point to evaluate the impact of this intervention. The incidences of early- and lateonset GBS infections during Period I (1995-2011) and Period II (2012-2019) were collected from each national register, covering 6,605,564 live births. Results: In Finland, a reduction of 58% in the incidence of early -onset GBS disease, corresponding to an incidence rate ratio (IRR) of 0.42 (95% CI: 0.34-0.52), was observed after 2012. At the same time, the pooled IRR of other Nordic countries was 0.89 (95% CI: 0.80- 1.0), specifically 0.89 (95% CI: 0.70-1.5) in Denmark, O .34 (95% CI: 0.15-0.81) in Iceland, 0.72 (95% CI: O .59-0.88) in Norway and 0.97 (95% CI: 0.85-1.1) in Sweden. Conclusions: In this ecological study of five Nordic countries, early -onset GBS infections were approximately halved following introduction of the SBP approach as compared with RBP.