BackgroundMaternal rectovaginal colonization with group B Streptococcus (GBS) is the most common pathway for GBS disease in mother, fetus, and newborn. This article, the second in a series estimating the burden of GBS, aims to determine the prevalence and serotype distribution of GBS colonizing pregnant women worldwide.MethodsWe conducted systematic literature reviews (PubMed/Medline, Embase, Latin American and Caribbean Health Sciences Literature [LILACS], World Health Organization Library Information System [WHOLIS], and Scopus), organized Chinese language searches, and sought unpublished data from investigator groups. We applied broad inclusion criteria to maximize data inputs, particularly from low- and middle-income contexts, and then applied new meta-analyses to adjust for studies with less-sensitive sampling and laboratory techniques. We undertook meta-analyses to derive pooled estimates of maternal GBS colonization prevalence at national and regional levels.ResultsThe dataset regarding colonization included 390 articles, 85 countries, and a total of 299924 pregnant women. Our adjusted estimate for maternal GBS colonization worldwide was 18% (95% confidence interval [CI], 17%–19%), with regional variation (11%–35%), and lower prevalence in Southern Asia (12.5% [95% CI, 10%–15%]) and Eastern Asia (11% [95% CI, 10%–12%]). Bacterial serotypes I–V account for 98% of identified colonizing GBS isolates worldwide. Serotype III, associated with invasive disease, accounts for 25% (95% CI, 23%–28%), but is less frequent in some South American and Asian countries. Serotypes VI–IX are more common in Asia.ConclusionsGBS colonizes pregnant women worldwide, but prevalence and serotype distribution vary, even after adjusting for laboratory methods. Lower GBS maternal colonization prevalence, with less serotype III, may help to explain lower GBS disease incidence in regions such as Asia. High prevalence worldwide, and more serotype data, are relevant to prevention efforts.

Group B Streptococcus is an important cause of disease in pregnant women, stillbirth, and infants. These first estimates show the magnitude and the potential impact of maternal vaccination.

Complications of preterm birth are the leading cause of deaths in children aged <5 years. Group B Streptococcus may be a preventable and important contributor to this burden.

Group B Streptococcus (GBS) is associated with invasive disease in utero and stillbirth. We estimated that 1% of all stillbirths in developed countries and 4% in Africa were associated with GBS.

From the limited data available, the incidence of maternal group B streptococcal (GBS) disease in developed countries appears lower than, but comparable to, the incidence of early-onset neonatal GBS disease. There are no published data from low- and middle-income contexts.

Group B Streptococcus is associated with multiple adverse pregnancy outcomes, yet previous epidemiology and interventions have mainly focused on neonatal invasive disease in high-income settings. We describe the rationale and approach for the first worldwide estimates of all relevant outcomes.

Highlights Most comprehensive review of Group B Streptococcal serotypes through 2018. First systematic review of Group B Streptococcal strain type and protein data. Theoretically candidate vaccines may protect against 93-99% disease-causing strains. More studies on GBS strains in low- and middle-income countries are needed.

BackgroundWe aimed to estimate, for the first time, the global burden of Group B Streptococcus (GBS), with regards to invasive disease in infants, as well as in pregnant and postpartum women, and fetal infection/stillbirth. Intrapartum antibiotic prophylaxis (IAP) is currently used for prevention of early onset infant disease in high-income contexts, but is difficult to implement globally, and may contribute to antimicrobial resistance. Maternal GBS vaccines are in development.MethodsFor 2015 live births, we used data from systematic reviews and meta-analyses (presented in separate papers in this GBS supplement) and a compartmental model to estimate:exposure to maternal GBS colonisation,cases of infant invasive GBS disease,deaths, anddisabilities.We applied incidence or prevalence data to estimate cases of maternal and fetal infection/stillbirth, and infants with invasive GBS disease presenting with neonatal encephalopathy (NE). We applied risk ratios to estimate numbers of preterm births attributable to GBS. Uncertainty was also estimated.Worldwide in 2015, we estimated 2 05 000 (uncertainty range [UR], 101000–327000) infants with early-onset disease and 1 14 000 (UR, 44000–326000) with late-onset disease, of whom a minimum of 7000 (UR, 0–19000) presented with neonatal encephalopathy. There were 90 000 (UR, 36000–169000) deaths in infants<3 months age, and, at least 10 000 (UR, 3000–27000) children with disability each year. There were 33 000 (UR, 13000–52000) cases of invasive GBS disease in pregnant or postpartum women, and 57 000 (UR, 12000–104000) fetal infections/stillbirths. Up to 3.5 million preterm births may be attributable to GBS. Africa accounted for 54% of estimated cases and 65% of all fetal/infant deaths. A maternal vaccine with 80% efficacy and 90% coverage could prevent 1 07 000 (UR, 20000–198000) stillbirths and infant deaths.ConclusionsOur conservative estimates suggest that GBS is a leading contributor to adverse maternal and newborn outcomes, with at least 4 09 000 (UR, 144000–573000) maternal/fetal/infant cases and 1 47 000 (UR, 47000–273000) stillbirths and infant deaths annually. An effective GBS vaccine could reduce disease in the mother, the fetus, and the infant.AcknowledgementAdditional authors include H Blencowe (1), S Cousens (1), CJ Baker, L Bartlett, C Cutland, MGGravett, PT Heath, M Ip, K Le Doare, SA Madhi, CE Rubens, SK Saha, SJ Schrag, A Sobanjo-ter Meulen, J Vekemans