by Monalisa Hassan
Session: Maternal Group B Strep Vaccines: Progress and Priorities
Efforts are being made to develop vaccines against a major contributor of stillbirths and infant deaths around the world: Group B Streptococcus
(GBS). Globally, GBS is the third leading cause of stillbirths, behind malaria and syphilis, according to a presentation
Monday at #TropMed17. New research from the London School of Hygiene & Tropical Medicine released at the ASTMH Annual Meeting
found that GBS infection causes an estimated 150,000 preventable stillbirths and infant deaths every year.
Dr. Ajoke Sobanjo-ter-Meulen, who leads the Bill & Melinda Gates Foundation’s maternal immunization initiative, which funded the GBS surveillance study, discussed the importance of developing and implementing universal GBS vaccination, especially in sub-Saharan Africa where there is a disproportionately high burden of disease.
GBS is part of the normal bacteria of the gastrointestinal tract and is carried by up to one-third of adults, usually with no symptoms. The new research found that an average of 18 percent of pregnant women worldwide carry – or are colonized with – GBS. According to the US Centers for Disease Control and Prevention (CDC), up to 25 percent of pregnant women in the US carry the bacteria. While GBS can live without causing the mother harm, if it is passed onto the unborn baby in utero, or to a newborn during labor, their immune systems cannot fight off the bacteria and the infection can be deadly.
The CDC strongly recommends GBS testing for pregnant women in the United States. For women who test positive, prophylactic administration of antibiotics intravenously during labor can prevent transmission to the baby. Dr. Meulen said that in the US, this practice has reduced mother to child transmission of GBS by 80 percent—a significant public health victory.
Around the world, this test and treat approach is often not feasible and GBS remains a primary cause of sepsis in newborns. Current data estimates GBS causes 90,000 infant deaths per year, with 57,000 of those deaths being stillbirths. Africa bears the highest burden with 65 percent of GBS-related stillbirths and infant deaths.
Sobanio-Ter Meulen discussed the potential value of a vaccine that in one shot would produce antibodies in pregnant women that would protect babies from transmission, because the cost and logistics of treatment are prohibitive in poor countries where the burden of GBS is high. For example, administering IV antibiotics during delivery is impossible because in many poor countries most women do not seek hospitalization during delivery.
Both GSK and Pfizer are among the pharmaceutical companies in the early stages of formulating GBS vaccines. While a vaccine is the ultimate goal, panelists also discussed the importance of widespread surveillance to fill the gap in data about stillbirths, preterm births, and maternal outcomes related to GBS. This information will be invaluable, they said, in ensuring equitable access to vaccination and prioritizing immunizations for populations that are particularly at risk.
This blog was written by Monalisa Hassan of Wake Forest University School of Medicine. She is attending #TropMed17 as a Benjamin H. Kean Travel Fellow in Tropical Medicine.