Background
Global rates of maternal GBS carriage and infant disease vary by region: highest in sub-Saharan Africa and lowest in Asia. Within-country variations by ethnicity have also been reported. We analysed data from a multicentre clinical trial to investigate whether variation in carriage rates underpin differential rates of disease in England.
Methods
Data from GBS3 trial sites undertaking recto-vaginal antenatal testing were obtained and enriched with maternal characteristics through linkage to NHS hospital data. Multivariable logistic regression of GBS carriage by maternal ethnicity adjusted for other key variables was undertaken.
Results
Data were obtained from 16,794 women tested in 7 sites between 2021-24. The overall carriage rate was 16.9%, with carriage increasing with age (15.6% in 20-24y; 19.1% in 40-44y). GBS carriage was 2.8% higher among the 20% most deprived compared to the 20% least deprived population quintile. Ethnicity data were available for 98.0% of women, with carriage rates highest in women of Black (20.5%) ethnicity followed by Asian (19.5%) and mixed (19.2%) ethnicity, substantially higher than women of white (15.8%) ethnicity. Variation was seen within Asian subgroups, ranging from 17.2% amongst Indian to 25.6% in Bangladeshi women. With adjustment for age, year and socioeconomic deprivation, GBS carriage was about twice as high (aOR=2.22; p=0.02) in women of mixed white/Black African heritage and (aOR=1.75; p<0.001) in Bangladeshi women compared to white counterparts.
Conclusion
We identified differences in GBS carriage by ethnicity not accounted for by age or deprivation. These mirror differences in UK infant and maternal GBS sepsis rates.