Estimates of the Burden of Group B Streptococcal Disease Worldwide for Pregnant Women, Stillbirths, and Children

Abstract

Background: We aimed to provide the first comprehensive estimates of the burden of group B Streptococcus (GBS), including invasive disease in pregnant and postpartum women, fetal infection/stillbirth, and infants. Intrapartum antibiotic prophylaxis is the current mainstay of prevention, reducing early-onset infant disease in high-income contexts. Maternal GBS vaccines are in development.

Methods: For 2015 live births, we used a compartmental model to estimate (1) exposure to maternal GBS colonization, (2) cases of infant invasive GBS disease, (3) deaths, and (4) disabilities. 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. We applied risk ratios to estimate numbers of preterm births attributable to GBS. Uncertainty was also estimated.

Results: Worldwide in 2015, we estimated 205000 (uncertainty range [UR], 101000-327000) infants with early-onset disease and 114000 (UR, 44000-326000) with late-onset disease, of whom a minimum of 7000 (UR, 0-19000) presented with neonatal encephalopathy. There were 90000 (UR, 36000-169000) deaths in infants <3 months age, and, at least 10000 (UR, 3000-27000) children with disability each year. There were 33000 (UR, 13000-52000) cases of invasive GBS disease in pregnant or postpartum women, and 57000 (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 107000 (UR, 20000-198000) stillbirths and infant deaths.

Conclusions: Our conservative estimates suggest that GBS is a leading contributor to adverse maternal and newborn outcomes, with at least 409000 (UR, 144000-573000) maternal/fetal/infant cases and 147000 (UR, 47000-273000) stillbirths and infant deaths annually. An effective GBS vaccine could reduce disease in the mother, the fetus, and the infant.

Keywords: group B Streptococcus; infection; maternal; newborn; stillbirth.

Figure 1.

Overview of the articles in this supplement to estimate the worldwide burden of group B Streptococcus. Adapted from Lawn et al [15]. Abbreviations: GBS, group B Streptococcus; NE, neonatal encephalopathy.

Figure 2.

Disease schema for outcomes of maternal group B Streptococcus colonization showing worldwide estimates for 2015. Adapted from Lawn et al [15]. Abbreviations: GBS, group B Streptococcus; NE, neonatal encephalopathy.

Figure 3.

Compartmental model for estimating cases of infant group B streptococcal disease, deaths, and disability. Abbreviations: EOGBS, early-onset group B Streptococcus; GBS, group B Streptococcus; IAP, intrapartum antibiotic prophylaxis; LOGBS, late-onset group B Streptococcus.

Figure 4.

Cases estimated for group B streptococcal (GBS) disease in pregnant/postpartum women, fetuses, and infants in 2015, by United Nations Sustainable Development Goal region. *Stillbirths represent a minimum estimate of fetal infection cases. More details are shown in Supplementary Figures 4, 11, and 12.

Figure 5.

Deaths estimated from group B streptococcal (GBS) disease for infants and stillbirths in 2015, by United Nations Sustainable Development Goal region. Maternal deaths not estimated. More details are shown in Supplementary Figures 6 and 12.

Figure 6.

Care and measurement gap estimating cases from incidence and prevalence data. Adapted from Lawn et al [15]. Triangulation of estimates from compartmental model compared to incidence data for invasive infant disease is detailed in Supplementary Figures 8 and 9. Abbreviation: GBS, group B Streptococcus.

Figure 7.

Scenarios of estimated cases of group B streptococcal (GBS) disease and deaths prevented with different intervention methods in a year. For worldwide clinical risk factor screening and intrapartum antibiotic prophylaxis (IAP) where microbiological screening was in place, this estimate was applied for that country. To facilitate comparison between the current situation and interventions, case fatality risks have been applied as at present (ie, a higher case fatality risk for deliveries without a skilled birth attendant).

Figure 8.

Group B streptococcal (GBS) serotypes colonizing mothers and causing disease in pregnant/postpartum women and infants. *Maternal colonization studies frequently reported Ia/Ib together, so these data are shown pooled. More details are shown in Supplementary Table 5.

Figure 9.

Summary of outcomes and measurement gaps in terms of deaths and disability from group B Streptococcus (GBS) in pregnant women, stillbirths, and infants worldwide in 2015. More details of cases and outcomes are shown in Supplementary Figures 4, 6, 7, 10–12.