20 million pregnant women with group B streptococcus carriage: consequences, challenges, and opportunities for prevention

Abstract

Purpose of review: Intrapartum antibiotic prophylaxis (IAP) is currently the only recommended preventive approach against clinical consequences of maternal Group B Streptococcus (GBS) colonization. In this review, we discuss new findings of total perinatal GBS burden and relative effectiveness of differing targeting of IAP, notably microbiology-based and risk factor-based screening, including potential limitations. Finally, we provide updates on maternal GBS vaccines and their potential cost-effectiveness in disease reduction.

Recent findings: Updated estimates of the burden of GBS related to pregnancy outcomes show (1) early-onset GBS disease incidence and deaths are high in some low- and middle-income countries where IAP has not been implemented and (2) late-onset GBS disease, preterm birth, and stillbirth, which are not preventable by IAP, remain a public health problem in both high and low-middle income settings. Observational evidence indicates that microbiology-based screening may be more effective than risk factor-based screening, but even in high-income countries, compliance is imperfect. To address the need for alternative prevention strategies, several maternal vaccine candidates are in clinical development, and modelling suggests these could be cost-effective in most scenarios.

Summary: Recent progress in GBS vaccine research holds promise of reducing the large and preventable burden of mortality and disability caused by GBS disease, especially in higher-burden settings where clinical and laboratory services may be limited. Importantly vaccines also hold potential to prevent GBS stillbirths and GBS-associated preterm births.

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FIGURE 1

Disease scheme for outcomes of Group B Streptococcus (GBS). The blue solid line arrows indicate later impairment, the black solid line arrows indicate death, and the blue dashed line arrows indicate healthy development. Figure adapted from Lawn JE et al. Clinical Infectious Diseases 2017 (2).

FIGURE 2

Definitions for GBS outcomes and the potential pathways of prevention comparing intrapartum antibiotic prophylaxis and maternal vaccines. Red indicates no evidence of protection, orange indicates unclear evidence of protection, yellow indicates evidence that it may offer some protection, light green indicates evidence of protection and dark green indicates strong evidence of protection. Definitions adapted from Lawn JE et al. Clinical Infectious Diseases 2017 (2).