Estimates done with development of global vaccination program in mind
by Molly Walker, Staff Writer, MedPage Today November 06, 2017

Action Points
• Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
• Note that a large meta-analysis has demonstrated high rates of maternal colonization with Group-B Streptococcus worldwide, which led to roughly 90,000 excess infant deaths annually.
• Antibiotic prophylaxis is highly effective at preventing GBS-associated disease in pregnancy, but is not universal.

BALTIMORE — More than 21 million pregnant women, or an average of 18% of women worldwide, are colonized with group B Streptococcus bacteria, or GBS, which contributes to stillbirth, preterm birth, and in some cases, death in their infants, researchers here estimated.
While India had the largest number of pregnant women with group B Streptococcus (over 2 million), the United States was fourth after China and Nigeria, with almost 1 million women colonized with the bacteria, reported Anna Seale, BMBCh, and Joy Lawn, BMedSci, both of the London School of Hygiene & Tropical Medicine, and colleagues.
In an 11-paper supplement published in Clinical Infectious Diseases, researchers detailed global estimates of the burden of group B Streptococcus bacteria among pregnant women, as well as the impact on infants and stillbirths, with the goal of moving closer to developing a vaccine.
The data were presented simultaneously at the American Society of Tropical Medicine & Hygiene annual meeting here.
While incidence of GBS previously focused mostly on infant cases in high-income countries, researchers described worldwide burden of the bacteria as “one of the great ‘black holes’ for public health worldwide.” They added that this is the first comprehensive study of the burden of group B Streptococcus including outcomes for both pregnant women and their babies.
Researchers also performed a series of systematic reviews and meta-analyses. To estimate colonization data for pregnant women, they analyzed 390 articles from 84 countries, for a total of almost 300,000 pregnant women. In the 188 studies that met CDC-recommended criteria, researchers found the average adjusted estimate for maternal group B Streptococcus global colonization was 18% (95% CI 17%-19%), with substantial regional variation, ranging from 11% in Eastern Asia to 35% in the Caribbean.
Seale & Lawn and colleagues also found that out of 15 examined studies, a single study estimated the incidence of “invasive maternal GBS disease” at 0.38% per 1,000 pregnancies. Pooled estimates found that two-thirds of cases were detected during labor and delivery or post-partum. The overall case fatality risk of pregnant or postpartum women experiencing invasive GBS was 0.20% (11 studies, 2 deaths, 890 cases), researchers said.
They then estimated the cases of group B Streptococcus colonization worldwide using a compartmental model, and found that of 140 million live births in 2015, 21.3 million infants were exposed to maternal GBS colonization at delivery. Moreover, they estimated there were 319,000 cases of infant invasive GBS disease worldwide, with 205,000 early-onset GBS disease and 114,000 late-onset GBS cases.
Researchers estimated 90,000 infant deaths due to group B Strep disease worldwide. Notably, they estimated 51,000 infant deaths due to early-onset GBS without access to healthcare. Stillbirth attributable to GBS disease was estimated at 57,000 cases, and the range of cases of preterm birth caused by GBS disease was 0 to 3.5 million.
Researchers noted that the treatment for pregnant women with group B Streptococcus is antibiotics prior to delivery, with 60 countries having an antibiotic policy for use in pregnancy that aims to prevent newborn GBS disease.
While intrapartum antibiotic prophylaxis prevented an estimated 29,000 infant deaths attributable to early-onset GBS and 3,000 deaths attributable to late-onset GBS, gaps in research remain.
“Existing recommendations should be implemented, but these are insufficient, and the number of affected families remain unacceptable,” co-author Johan Vekemans, MD, of the World Health Organization, said in a statement. “It is now essential to accelerate the GBS vaccine development activities.”
Indeed, researchers estimate that with worldwide maternal vaccination, a vaccine with 80% efficacy and 50% coverage would prevent an estimated 127,000 infant and maternal cases of GBS, 23,000 stillbirths, and 37,000 infant deaths.
Vekemans added that a “comprehensive evaluation” is needed on the cost-effectiveness of a vaccine against group B Streptococcus, and work is needed to strengthen existing maternal immunization programs worldwide.

This supplement was supported by the Bill & Melinda Gates Foundation.
Authors disclosed support from the Bill & Melinda Gates Foundation, Wellcome Trust, Medical Research Council UK, the Thrasher Foundation, the Meningitis Research Foundation, the NIH, Sequirus Inc, CureVac Inc, Pfizer Inc., Novartis, Belpharma Eumedica, GlaxoSmithKline and Minervax.
Members of the Expert Advisory Group received reimbursement for travel expenses to attend working meetings related to this series.
• Reviewed by F. Perry Wilson, MD, MSCE Assistant Professor, Section of Nephrology, Yale School of Medicine and Dorothy Caputo, MA, BSN, RN, Nurse Planner
last updated 11.07.2017
• Primary Source
American Society of Tropical Medicine & Hygiene
Source Reference: Seale AC “Estimating the global burden of group B Streptococcus in pregnant women, stillbirths and children to inform vaccine development” ASTMH 2017; Session 6.
• Secondary Source
Clinical Infectious Diseases
Source Reference: Seale AC, Lawn JE “The burden of group B Streptococcus worldwide for pregnant women, stillbirths and children” Clin Infect Dis 2017; 65(2).