Estimating the burden of invasive Group B Streptococcal disease in young infants in southern mainland China: an observational study

Objectives: To estimate the incidence, case fatality ratio and serotypes associated with early-onset (EOD) and late-onset (LOD) invasive GBS disease in infants in southern mainland China. Methods: During the six-month study period, infants aged <= 90 days with culture-confirmed GBS disease born in the study hospitals or elsewhere, but presenting to a study hospital, were enrolled. GBS-positive cultures were genotyped, serotyped and sequence typed. The incidence rate was calculated for infants born in the study hospitals, and case fatality ratio and causative serotypes identified for all enrolled GBS cases. Results: Ten cases were enrolled: 2 EOD cases born in the study hospitals and 8 LOD cases born elsewhere. Incidence rate was 0.28 (95% confidence interval: 0.08-1.03, n = 2/7061 successfully followed-up consenting subjects); no cases resulted in fatality. In the 8 GBS isolates available for typing, 4 serotypes (Ia, Ib, III and V) and 5 multi-locus sequence types (1, 10, 12, 17 and 23) were identified. Conclusions: This is the first study specifically investigating the incidence of GBS invasive disease in infants in southern mainland China. Incidence and case fatality were low but further research is needed in larger, more diverse cohorts to estimate disease burden for the broader Chinese population.