A new report calls for developing maternal vaccines against Group B streptococcus

A new reportfrom the World Health Organization (WHO) and the London School of Hygiene Tropical Medicine (LSHTM) reveals the alarming global impact of Group B streptococcus (GBS). This bacterium - harmless for most pregnant women who carry it - can be extremely serious when it passes to the baby during pregnancy, birth or in the early weeks of life.

The report, presented during the ISAAD conference and accompanied by a series of papers published as a supplement in the journal Clinical Infectious Diseases, is the first to quantify the major contribution of GBS to preterm births and neurological impairments.

“ISGlobal and the Manhiça Health Research Center (CISM) participated in this multi-site study, in which GBS survivors and healthy controls from the last two decades were recruited and assessed for their neurocognitive outcomes, evidencing the hidden burden of long-term neurological sequelae”, explains Quique Bassat, ICREA researcher at ISGlobal and senior author of one of the papers in the series. CISM, in Mozambique, was one of the four recruiting centres, alongside South Africa, India, and Argentina.

The report highlights that the global burden of GBS is far higher than previously recognised. In 2020, 19.7 million pregnant women (that is, 15% of pregnant women worldwide) were estimated to be colonised with GBS, leading to 518,000 preterm births, 91,000 newborn deaths and 40,000 infants living with neurological impairment.

Currently, the way to avoid GBS disease in newborns is a microbiological screening during the later stages of pregnancy followed by antibiotic prophylaxis to those women found to be infected. However, the largest burden of GBS is in low- and middle-income countries in sub-Saharan Africa and South-Eastern Asia, where screening and antibiotic administration during childbirth are most challenging to implement.

Hence, the urgent need to develop maternal vaccines against GBS, says the report. Vaccinating 70% of pregnant women would avert over 50,000 GBS deaths, 170,000 preterm births and generate net benefits of 17 billion USD. The report also highlights important data gaps. For example, the causes of stillbirths are frequently under-investigated and could further increase the total burden of deaths and disease caused by GBS.

Developing a GBS vaccine was proposed 30 years ago, and several vaccine candidates have been in development for the last decades, but none are yet available. A maternal GBS vaccine would have profound benefits in countries worldwide, argue the report authors.

Reference

Clinical Infectious Diseases Supplement on Group B streptococcus (GBS)