Prevalence and serotype distribution of group B Streptococcus in León, Nicaragua

Dr Nadja Alexandra Vielot, Postdoctoral Research Associate
Family Medicine, University of North Carolina at Chapel Hill (USA)
Nadja Vielot

Professor Samuel Vilchez, National University of Nicaragua, León (Nicaragua)
Professor Neil French, University of Liverpool (UK)

While under-five mortality has steadily declined since 1990, declines in neonatal mortality are less pronounced. Group B Streptococcus (GBS) disease is the most common cause of infant sepsis and meningitis, causing approximately 90,000 deaths and 56,000 stillbirths globally in 2015. Mothers with rectovaginal GBS colonization can vertically transmit GBS to infants during labour, causing early-onset GBS disease (EOD). To prevent EOD, 60 countries have instituted national policies to provide intrapartum antibiotic prophylaxis (IAP) to women with GBS colonization or who meet certain GBS risk criteria. However, lack of universal GBS screening, particularly in low- and middle-income countries (LMIC) complicates EOD prevention. Further, late-onset GBS disease (LOD) can occur with horizontal mother-infant GBS transmission after the first week of life, and cannot be prevented with IAP. A prophylactic GBS vaccine administered late in pregnancy could prevent infant GBS infection.

Investigational GBS vaccines have shown safety and immunogenicity in Phase 2 trials. However, GBS serotype distribution in LMIC are largely unknown. We propose a study in León, Nicaragua, to guide serotype-specific GBS prevention strategies. We will first collect rectovaginal samples from pregnant women to characterize GBS serotype distribution and serotype coverage of candidate pentavalent and hexavalent GBS vaccines. Next, we will describe the frequency and patterns of co-colonization with multiple GBS serotypes in colonized women. This data will improve estimates of serotype-specific GBS vaccine effectiveness, providing evidence-based guidance for GBS vaccine development and policy-making.